Added 'Performance Tuning Your Builds' article to documentation.

Summary: Document performance tuning

Test Plan: Ran soy locally.
diff --git a/docs/__common.soy b/docs/__common.soy
index ea14e53..e2eb3c0 100644
--- a/docs/__common.soy
+++ b/docs/__common.soy
@@ -34,7 +34,7 @@
 <html>
 <head prefix="og: http://ogp.me/ns# fb: http://ogp.me/ns#">
   <title>{$fullTitle}</title>
-  <link type="image/png" rel="icon" href="{ROOT}favicon.png" />
+  <link type="image/png" rel="icon" href="{ROOT}static/favicon.png" />
   <meta http-equiv="content-type" content="text/html;charset=utf-8">
   {if $prettify}
     <link type="text/css"
@@ -43,7 +43,7 @@
           >
   {/if}
   // List buck.css second to override prettify.
-  <link type="text/css" rel="stylesheet" href="{ROOT}buck.css">
+  <link type="text/css" rel="stylesheet" href="{ROOT}static/buck.css">
 
 // Google Analytics.
 <script>
@@ -80,7 +80,7 @@
 
 // Image copied from https://github.com/blog/273-github-ribbons
 <a href="https://github.com/facebook/buck">
-  <img id="fork" src="{ROOT}fork_me.png" alt="Fork me on GitHub">
+  <img id="fork" src="{ROOT}static/fork_me.png" alt="Fork me on GitHub">
 </a>
 
 <div id="fb-root"></div>
@@ -130,6 +130,7 @@
   <ul>
     <li><a href="{ROOT}concept/what_makes_buck_so_fast.html">What Makes Buck so Fast?</a>
     <li><a href="{ROOT}concept/troubleshooting.html">Troubleshooting</a>
+    <li><a href="{ROOT}about/performance_tuning.html">Performance Tuning</a>
     <li><a href="{ROOT}concept/faq.html">FAQ</a>
   </ul>
   <li><span class="{css toc_header}">Concepts</span>
diff --git a/docs/about/performance_tuning.soy b/docs/about/performance_tuning.soy
new file mode 100644
index 0000000..10e95b4
--- /dev/null
+++ b/docs/about/performance_tuning.soy
@@ -0,0 +1,65 @@
+{namespace buck.performance}
+
+/***/
+{template .soyweb}
+  {call buck.page}
+    {param title: 'Performance Tuning' /}
+    {param content}
+
+<h2>Performance Tuning Your Builds</h2>
+
+Buck <a href="{ROOT}concept/what_makes_buck_so_fast.html">does a lot of work</a>
+{sp} to make builds as fast as possible, and we also give developers tools to
+figure out where the time is being spent inside of their builds.
+
+<h2>Super Console</h2>
+
+<img id="super_console_sample"
+     src="{ROOT}static/buck-build-15fps.gif"
+     alt="Chrome Tracing Sample">
+
+<p>
+
+When running Buck in an{sp}
+<a href="http://en.wikipedia.org/wiki/ANSI_escape_code">Ansi</a> compliant
+terminal, Buck displays the break down of
+what each thread is doing, updated every 100ms, in what we affectionately call
+"SuperConsole."  While a build is running, this gives developers a good idea of
+what Buck is spending its time doing, and can often help people spot issues in
+their builds.  If you want to see what happened after the fact or to have a
+trace you can send around your team, use Chrome Tracing.
+
+<h2>Chrome Tracing</h2>
+
+<img id="chrome_sample"
+     src="{ROOT}static/buck_chrome_sample.png"
+     alt="Chrome Tracing Sample">
+
+The Chrome team has built an awesome framework for viewing performance traces
+right inside of{sp}
+<a href="http://www.chromium.org/developers/how-tos/trace-event-profiling-tool">
+Chrome</a>.  You can access this by going to <code>chrome://tracing</code> in
+your browser.  Consult the trace viewer's
+{sp}<a href="https://code.google.com/p/trace-viewer/">project page</a> for more
+information on the trace viewer and the file format.
+
+<p>
+
+After Buck is done with each build, it will produce a Chrome Trace file that can
+be loaded up in <code>chrome://tracing</code> in the directory
+{sp}<code>buck-out/log/traces/</code>.  Buck will save a file in the format
+<code>build.[timestamp].trace</code>, and then create a symlink from the most
+recent trace to <code>build.trace</code>.
+
+<p>
+
+To load up this trace, visit <code>chrome://tracing</code> inside of Chrome, and
+hit "Load".  Load the trace file of interest, and look around to see where time
+was spent.  Each row represents a different thread, and all of the steps taken
+for a given rule are logged underneath that rule.  Additionally, we log
+information about how the rule was built and and the rule key for each artifact
+fetch.  Press <em>?</em> to get the help menu for the Chrome Trace Viewer.
+
+    {/param}  // content
+  {/call} // buck.page
+{/template}
diff --git a/docs/concept/buckconfig.soy b/docs/concept/buckconfig.soy
index 48cdc9f..4980d23 100644
--- a/docs/concept/buckconfig.soy
+++ b/docs/concept/buckconfig.soy
@@ -250,6 +250,19 @@
   post_process = ./scripts/post_process_buck_project.sh
 </pre>{/literal}
 
+<h2>[log]</h2>
+
+This section controls how buck will log information about builds for later
+inspection.
+
+{literal}<pre>
+[log]
+  max_traces = 25
+</pre>{/literal}
+
+Will limit buck to creating, at most, 25{sp}
+<a href="{ROOT}about/performance_tuning.html">Chrome Traces</a>.
+
     {/param}
   {/call}
 {/template}
diff --git a/docs/soy2html.py b/docs/soy2html.py
index 6f7c854..fe7a883 100644
--- a/docs/soy2html.py
+++ b/docs/soy2html.py
@@ -51,6 +51,7 @@
       elif (file_name.endswith('.css') or
             file_name.endswith('.js') or
             file_name.endswith('.png') or
+            file_name.endswith('.gif') or
             file_name.endswith('.html')):
         #  Copy the static resource to output_dir.
         relative_path = os.path.join(root, file_name)
diff --git a/docs/static/buck-build-15fps.gif b/docs/static/buck-build-15fps.gif
new file mode 100644
index 0000000..0e47bd5
--- /dev/null
+++ b/docs/static/buck-build-15fps.gif
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diff --git a/docs/buck.css b/docs/static/buck.css
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rename from docs/buck.css
rename to docs/static/buck.css
diff --git a/docs/static/buck_chrome_sample.png b/docs/static/buck_chrome_sample.png
new file mode 100644
index 0000000..97750ef
--- /dev/null
+++ b/docs/static/buck_chrome_sample.png
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diff --git a/docs/favicon.png b/docs/static/favicon.png
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rename from docs/favicon.png
rename to docs/static/favicon.png
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diff --git a/docs/fork_me.png b/docs/static/fork_me.png
similarity index 100%
rename from docs/fork_me.png
rename to docs/static/fork_me.png
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