Update gradle version to 3.0.0-beta5.

Android Studio refuses to build with the current beta4 version.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=171129696

build.gradle

@@ -17,7 +17,7 @@ buildscript {
         google()
         google()
     }
     }
     dependencies {
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.0.0-beta4'
+        classpath 'com.android.tools.build:gradle:3.0.0-beta5'
         classpath 'com.novoda:bintray-release:0.5.0'
         classpath 'com.novoda:bintray-release:0.5.0'
     }
     }
     // Workaround for the following test coverage issue. Remove when fixed:
     // Workaround for the following test coverage issue. Remove when fixed: