Let test compile & resource processing run at the end of "assemble" task

Previous commit was fine for test classes, however java test resources are not processed during the `testCompileTask`.

Note: in order for Android Studio to add your resources to class path when running tests, you need to add them manually to dependencies:

1. Go to module dependencies
2. Click Add --> Jars or directories
3. Choose resource directory (e.g. `YourProject/build/resources/testVariantName`)
4. In next dialog choose "Classes"
5. Set scope to "Test"
Increment version for local installs