Use static imports for Assume.assumeTrue() throughout the codebase.

Test Plan: Sandcastle builds.
diff --git a/test/com/facebook/buck/shell/ShBinaryRuleIntegrationTest.java b/test/com/facebook/buck/shell/ShBinaryRuleIntegrationTest.java
index b4c0c68..8e8836d 100644
--- a/test/com/facebook/buck/shell/ShBinaryRuleIntegrationTest.java
+++ b/test/com/facebook/buck/shell/ShBinaryRuleIntegrationTest.java
@@ -19,6 +19,7 @@
 import static org.hamcrest.Matchers.containsString;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertThat;
+import static org.junit.Assume.assumeTrue;
 
 import com.facebook.buck.testutil.integration.DebuggableTemporaryFolder;
 import com.facebook.buck.testutil.integration.ProjectWorkspace;
@@ -30,7 +31,6 @@
 import com.google.common.base.Charsets;
 import com.google.common.io.Files;
 
-import org.junit.Assume;
 import org.junit.Rule;
 import org.junit.Test;
 
@@ -46,7 +46,7 @@
   @Test
   public void testTrivialShBinaryRule() throws IOException {
     // sh_binary is not available on Windows. Ignore this test on Windows.
-    Assume.assumeTrue(Platform.detect() != Platform.WINDOWS);
+    assumeTrue(Platform.detect() != Platform.WINDOWS);
     ProjectWorkspace workspace = TestDataHelper.createProjectWorkspaceForScenario(
         this, "sh_binary_trivial", temporaryFolder);
     workspace.setUp();
@@ -63,7 +63,7 @@
   @Test
   public void testShBinaryWithResources() throws IOException {
     // sh_binary is not available on Windows. Ignore this test on Windows.
-    Assume.assumeTrue(Platform.detect() != Platform.WINDOWS);
+    assumeTrue(Platform.detect() != Platform.WINDOWS);
     ProjectWorkspace workspace = TestDataHelper.createProjectWorkspaceForScenario(
         this, "sh_binary_with_resources", temporaryFolder);
     workspace.setUp();
@@ -83,7 +83,7 @@
   @Test
   public void testShBinaryCannotOverwriteResource() throws IOException {
     // sh_binary is not available on Windows. Ignore this test on Windows.
-    Assume.assumeTrue(Platform.detect() != Platform.WINDOWS);
+    assumeTrue(Platform.detect() != Platform.WINDOWS);
     ProjectWorkspace workspace = TestDataHelper.createProjectWorkspaceForScenario(
         this, "sh_binary_with_overwrite_violation", temporaryFolder);
     workspace.setUp();
diff --git a/test/com/facebook/buck/step/fs/SymlinkFileStepTest.java b/test/com/facebook/buck/step/fs/SymlinkFileStepTest.java
index 0d9075b..ba56760 100644
--- a/test/com/facebook/buck/step/fs/SymlinkFileStepTest.java
+++ b/test/com/facebook/buck/step/fs/SymlinkFileStepTest.java
@@ -18,6 +18,7 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assume.assumeTrue;
 
 import com.facebook.buck.step.ExecutionContext;
 import com.facebook.buck.step.TestExecutionContext;
@@ -26,7 +27,6 @@
 import com.google.common.base.Charsets;
 import com.google.common.io.Files;
 
-import org.junit.Assume;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
@@ -69,7 +69,7 @@
 
   @Test
   public void testReplaceMalformedSymlink() throws IOException, InterruptedException {
-    Assume.assumeTrue(Platform.detect() != Platform.WINDOWS);
+    assumeTrue(Platform.detect() != Platform.WINDOWS);
 
     // Run `ln -s /path/that/does/not/exist dummy` in /tmp.
     ProcessBuilder builder = new ProcessBuilder();
diff --git a/test/com/facebook/buck/zip/ZipStepTest.java b/test/com/facebook/buck/zip/ZipStepTest.java
index e6ad4ef..54a5e2b 100644
--- a/test/com/facebook/buck/zip/ZipStepTest.java
+++ b/test/com/facebook/buck/zip/ZipStepTest.java
@@ -20,6 +20,7 @@
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assume.assumeTrue;
 
 import com.facebook.buck.step.TestExecutionContext;
 import com.facebook.buck.testutil.Zip;
@@ -27,7 +28,6 @@
 import com.google.common.collect.ImmutableSet;
 import com.google.common.io.Files;
 
-import org.junit.Assume;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
@@ -109,7 +109,7 @@
   @Test
   public void mustIncludeTheContentsOfFilesThatAreSymlinked() throws IOException {
     // Symlinks on Windows are _hard_. Let's go shopping.
-    Assume.assumeTrue(Platform.detect() != Platform.WINDOWS);
+    assumeTrue(Platform.detect() != Platform.WINDOWS);
 
     File parent = tmp.newFolder("zipstep");
     File out = new File(parent, "output.zip");