Fix issue #3 -added core contributors to README.md
Implement user routes that use the name

Fix issue #15

-Added the friendly_id gem and extended the model
-The controller can look up the User by id or name
Add a show view for User

For issue #15

-The nav bar now links to the current signed in user.
-The show route displays the user's twitter handle.
Merge pull request #16 from kstradley/master

Addressed Issues #3 & #15