get /obligations returns json

:warning: Don't Merge Yet, will currently break prod :warning: 

I have changed GET /obligations so that it will return the obligations as JSON in order to keep it consistent with the rest of the API and make parsing much easier on the client side than it currently is.  

Unless anyone has any objections or issues with the following code my plan would be to refactor the existing calls to GET /obligations (only one I can think of off hand would be in the schedule for putting the obligations into the calendar) tomorrow and include the refactored versions as part of this pull request and merge it all at once.

Just want to check and make sure nobody is currently doing anything with those calls that my refactoring could hurt.

@KyleBrownCS @Dayton1992 @frezen88 @bencatalan