add subscribe
Merge branch 'master' of https://github.com/mazilian/lms299

Conflicts:
	controllers/notes.py
Merge branch 'master' of https://github.com/mazilian/lms299

 Please enter a commit message to explain why this merge is necessary,
merge
Merge branch 'master' of https://github.com/mazilian/lms299
Merge branch 'master' of https://github.com/mazilian/lms299
Merge branch 'master' of https://github.com/mazilian/lms299
add relevant function