Upgrade gradle plugin / wrapper

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=167579719

build.gradle

@@ -19,7 +19,7 @@ buildscript {
         }
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:2.3.3'
+        classpath 'com.android.tools.build:gradle:3.0.0-beta4'
         classpath 'com.novoda:bintray-release:0.5.0'
     }
     // Workaround for the following test coverage issue. Remove when fixed:

gradle/wrapper/gradle-wrapper.properties

-#Wed Jul 12 10:31:13 BST 2017
+#Tue Sep 05 13:43:42 BST 2017
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.0.1-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.1-all.zip