Merge pull request #22 from nlambson/master

Added support for Announcements which are basically Discussion Topics
Merge pull request #23 from nlambson/master

Header declaration for new Announcements fetch method
Reactivate the client login process
Update sample code to work with the new reactive APIs
Update README.md

update the readme's info on login.
Merge pull request #24 from jarsen/master

Reactive Login + Update Example Project
Add header to load client from keychain.
Merge remote-tracking branch 'instructure/CanvasKit/master'
Merge pull request #25 from jarsen/master

Add header to load client from keychain
Adds course permissions update endpoint
Updated to support conversation messages

Includes changes to support assignment submissions interleaved
with submissions
adds attachment ids to createMessage:
Allow a conversation to merge in sent message
Sets the correct context on assignments for todo items
Adding read_state to CKIActivityStreamItem
Adds a couple of conversation related endpoints.
Implements path method for CKITodoItem
Uses the assignment id for the todo items path
I have fixed this bug at least 4 times
Add URL property to CKIActivityStreamItem