Replaced Utilities.isNycOrAbove() with version code check.

- Instead of using reflection to check if N is present, we now use
  Build.VERSION.SDK_INT >= Build.VERSION_CODES.N.
- Other places that used reflection to use N APIs have also been
  cleaned up.

Bug: 22942492
Change-Id: Ia7b981cae375e800bcc8f0c54aec48e0c8c076da
diff --git a/build.gradle b/build.gradle
index b9a990f..00bed8b 100644
--- a/build.gradle
+++ b/build.gradle
@@ -3,7 +3,7 @@
         mavenCentral()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:1.5.0'
+        classpath 'com.android.tools.build:gradle:2.1.0'
         classpath 'com.google.protobuf:protobuf-gradle-plugin:0.7.0'
     }
 }