Adds Setup instructions to README and rake task for user setup

I was setting up critic critic on my machine and ran across some essentials for setup.

1. The setup instructions were incomplete: database must be seeded and a user created before app is usable locally
2. I created a rake task for creating a user. A name can be specified or will default to 'Dustin'
3. Added description of the application to the readme and modified formatting

None of these changes affected the test suite.