Scaffold User

...with first & last name, email, bio, fb id, google id, and auth token.

Important files to note:
db/migrate/...
app/models/...
config/routes.rb
Consider not having user contain all of these ids.
Consider instead setting up an Identity model:

```
class CreateIdentities < ActiveRecord::Migration
  def change
    create_table :identities do |t|
      t.references :user, index: true
      t.string :provider
      t.string :uid
      t.string :token
      t.string :secret
      t.json :info
    end
    add_index :identities, [:provider, :uid], unique: true
  end
end
```