Helen/synchonous features with socketio

[lihelennn]

Sync features

• Adding socket.io setup
• Adding emits when new thread or new reply comes in
• Add POST/annotations/new_annotation endpoint to post new annotation for sync stuff
• Add POST/annotations/new_reply/:id endpoint to post new reply for sync stuff
• Add GET/annotations/specific_thread endpoint to query for a specific thread
• Add GET/annotations/myCurrentSection endpoint to query for section user is in for a specific class