Changed an AssignmentGroup's group_weight to use a double instead of a long.

group_weights can use decimal places and will error out on retrofit for courses with group_weights
using decimal precision.
Updated the build tools version to 21.1.0
Added support for gpa_scale grading type
Added support for gpa_scale grading type in canvasapi
Add RxJava
Added not_graded as a gradingType
Updated gradle files to next version of gradle.
Stop tracking .iml files
Update gradle
Added sortable name to Users
Fixed bugs and unused imports found and various issues.
Fixed some encoding errors recently introduced.
Fixed a spelling error.
Adds RxJava method for uploading avatar images
Merge remote-tracking branch 'upstream/master'

Conflicts:
	src/main/java/com/instructure/canvasapi/api/AssignmentAPI.java
fix issue with unread count
Merge pull request #99 from amozoss/master

fix issue with unread count