Adapt README.md to a Bazel in-tree build

While the Buck build has been removed, the README.md instructions
were still stuck with it. Adapt all the instructions to reflect
what is needed to successfuly build the plugin with Bazel
using a Gerrit in-tree style plugin build process.

Change-Id: I32282c89ba799ccbf09e9023eb5c33ee5eebbff9
diff --git a/README.md b/README.md
index 0c73b9f..f487d62 100644
--- a/README.md
+++ b/README.md
@@ -23,20 +23,28 @@
 
 * `linux`
 * `java-1.8`
-* `Buck`
+* `Bazel`
 
 Build
 ---------------------
+Kafka plugin can be build as a regular 'in-tree' plugin. That means that is required to
+clone a Gerrit source tree first and then to have the Kafka plugin source directory into
+the /plugins path. Additionally, the plugins/external_plugin_deps.bzl file needs to be
+updated to match the Kafka plugin one.
 
-Clone or link this plugin to the plugins directory of Gerrit's source
-tree, and issue the command:
+    git clone --recursive https://gerrit.googlesource.com/gerrit
+    git clone https://gerrit.googlesource.com/plugins/kafka-events gerrit/plugins/kafka-events
+    cd gerrit
+    rm plugins/external_plugin_deps.bzl
+    ln -s ./kafka-events/external_plugin_deps.bzl plugins/.
 
+To build the kafka-events plugins, issue the command from the Gerrit source path:
 
-    buck build plugins/kafka-events
+    bazel build plugins/kafka-events
 
 The output is created in
 
-    buck-out/gen/plugins/kafka-events/kafka-events.jar
+    bazel-genfiles/plugins/kafka-events/kafka-events.jar
 
 Minimum Configuration
 ---------------------