Allow id to be returned in to_json

Devise changes the serializable_hash so it does not include any attributes that are not accessible (https://github.com/plataformatec/devise/blob/master/lib/devise/models/serializable.rb). This commit puts id back in the user's serializable hash.
Merge pull request #1 from piotrj/user_json

Allow id to be returned in to_json
Add sign in view and flash messages with bootstrap styling
Update README
Improve in-app documentation

Remove the duplication between readme and app's index. Now it renders
the readme instead, using markdown and syntax highlighting.

Also includes necessary javascript to make topbar headers more useful.
Update doorkeeper from github
Add doorkeeper gem from rubygems
Update oauth access grants table
Update gem, initializer and database
Limit index list and add create action
Add sample scopes
Update doorkeeper gem
Shorten token expiration time
Remove test folder
Add rspec rails
Install rspec files
Add credentials controller tests
Introduce #recent scope
Respond with correct namespace
Add profiles controller spec