Adds support for dynamic button positioning

If the showcase is on the bottom right quadrant of the screen, we move the action button to the bottom left to avoid them conflicting with each other.
This is handled automatically by ``ShowcaseView``. Nothing has changed in the API side. Please let me know if you think this is not best way to handle and I can change it accordingly.

I updated the Animations activity in the demo app to demostrate this change.

I also had to disable the test plugin and mvn push since they are not compatible yet with latest gradle build tools.