Move to Gradle 3.3 and enable Gradle Parellization.

org.gradle.parallel=true speeds up ./gradle clean assemble from
1 minute 56 seconds to 28 seconds on my machine.

Test: ./gradlew clean assemble still works
Change-Id: I88437e2b6400981f9451ab9271da949966283d81
diff --git a/gradle.properties b/gradle.properties
index 34b3995..fb870a9 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -1,3 +1,4 @@
 org.gradle.jvmargs=-Xmx3g
 org.gradle.daemon=true
-org.gradle.configureondemand=true
\ No newline at end of file
+org.gradle.configureondemand=true
+org.gradle.parallel=true