Merge pull request #25 from bradylarson/master

Added polling APIs. Get a single section. Null check
Upgrade to Retrofit 1.5.1

No breaking changes found.
Merge pull request #26 from nbutton23/update-retrofit1.5.1

Upgrade to Retrofit 1.5.1
Added needs_grading_per_section_map to assignments. Also fixed some unintuitive logic inside submission object inside get_grader_id.
Merge pull request #27 from hhoang/master

Added needs_grading_per_section_map to assignments. Also fixed some unin...
Update Gradle
Updated the build.gradle file to min-sdk 9 (2.3)

The readme already says that we only support min-sdk 9
Added a favorites object for favoriting courses, added api calls to CoursesAPI
Merge pull request #28 from nbutton23/master

Update Gradle
Merge pull request #29 from matthewrice345/Favorites

Added a favorites object for favoriting courses, added api calls to Cour...
Added created date and user id to PollSubmission