add Google Play Game Service.
update resources
update
add two buttons
add two buttons
fix a crash
integrate the google play game service
update strings
add leaderboards
refactor the source code, use fragment
refactor the source code.
fix onResume
adjust ui
Merge branch 'master' of https://github.com/pjq/pushup

Conflicts:
	PushUp/src/main/AndroidManifest.xml
	PushUp/src/main/java/me/pjq/pushup/MainActivity.java