Update gradle tools to 3.0.0 and support library to 27.0.0.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=173645345

build.gradle

@@ -17,7 +17,7 @@ buildscript {
         google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.0.0-beta7'
+        classpath 'com.android.tools.build:gradle:3.0.0'
         classpath 'com.novoda:bintray-release:0.5.0'
     }
     // Workaround for the following test coverage issue. Remove when fixed:

constants.gradle

@@ -21,7 +21,7 @@ project.ext {
     targetSdkVersion = 26
     buildToolsVersion = '26.0.2'
     testSupportLibraryVersion = '0.5'
-    supportLibraryVersion = '26.1.0'
+    supportLibraryVersion = '27.0.0'
     playServicesLibraryVersion = '11.4.2'
     dexmakerVersion = '1.2'
     mockitoVersion = '1.9.5'