ADDING O-Auth to TaskListRails

[Trishthedish]

https://github.com/AdaGold/standalone-exercises/blob/master/tasklistrails-oauth.md
Accomplished Phase 1 and will continue to work on Phase 2 and 3 over the weekend.

@Hamled

Phase 1: Setting up OAuth
Following the steps in the Textbook curriculum, add OAuth to your TaskListRails Application and enable a user to log in from the homepage.

Requirements:
Have a button on the home page for the user to log in
The log in button shall turn in to a log out button when the user is logged in

All other requirements from in-class notes apply:
Managed via session
SessionsController
User model

Phase 2: User Authorization
Requirements:
Ensure that users who are not authenticated see a welcome message and a link to authenticate. No other pages should be viewable by the guest user.
Ensure that Users who are authenticated see the normal Tasklist page.
Build Automated Tests on the User Model.

Phase 3: Modifying The Task Model & Controller
Requirements:
Modify the Task Model to create a relation to the User Model. A User should have many tasks and each Task should belong to a User.
Modify the Task Controller index and show actions so that a user only sees tasks that belong to them.
Modify the Task Controller's edit and update method to ensure that the user cannot edit a task that does not belong to them.
Modify the new and create actions for the task controller so that the new task created will belong to the current user.
Ensure that unauthenticated users cannot create tasks and are redirected to login.