join session functionality

-'add session' button changes to 'view session' if user has joined a
session (takes user to details page of current session)
-detailsPage detects if user has joined the currently viewed session and
changes 'join' button to 'leave'
-'leave' functionality doesn't work yet
Merge branch 'master' of https://github.com/JoePelz/studyStorm

Conflicts:
	js/queries.js