#41: /participants/:membername/:challenge_id/deliverable (put)
#26: Implement /challenges/:challenge_id (put)
Merge branch 'master' into aluxian
#18: Implement /accounts/:membername/preferences (put)
Merge branch 'master' into aluxian
#37: Implement /participants/:membername/:challenge_id (post)
#38: Implement /participants/:membername/:challenge_id (put)
#40 Implement /participants/:membername/:challenge_id/deliverables (post)
Moved endpoint to correct file
Switched implementation to pg (POST /participants/:membername/:challenge_id/deliverables)
Made data parameter accept json for endpoint PUT /participants/:membername/:challenge_id/deliverables
added work for sessions
Closes #41, closes #26, closes #18, closes #37, closes #38, closes #40