bug fix - spiral 2 final
Merge branch 'master' of
https://github.com/VictorChenLi/BatonStudentAndroid.git

Conflicts:
	src/ca/utoronto/ece1778/baton/screens/MainScreenActivity.java
add teacher_id in join activity
Merge branch 'master' of https://github.com/VictorChenLi/BatonStudentAndroid.git