Refactored cucumber tests
Add presence validation to image_url in palette
Refactored model/controller specs
Refactor Palette Model
Refactored PaletteSet model
Refactor PaletteSetsController

* Also changed 'tumblr_username' field name in view to 'source',
  in order to match the 'source' attribute in the PaletteSet
  model
    * Necessitated updating the controller spec and the generate
      palette features
Wrote user favorite features
Fixed template

Forgot to indent li's under the ul
Started implementation of "Favorite" feature

* Added a "Favorite" button to PaletteSet#show view
* Started a UsersController#favorite method
* Added POST /favorite/:id to routes
  * id is the id of the PaletteSet to be favorited
Merge remote bc I fucked up a rebase

Merge remote-tracking branch 'origin/master'

Conflicts:
	colors/app/models/palette.rb
	colors/app/models/palette_set.rb
	colors/features/generate_palette_for_a_blog.feature
	colors/features/step_definitions/palette_set_steps.rb
	colors/features/step_definitions/user_steps.rb
	colors/features/support/world_extensions.rb
	colors/features/user_login.feature
	colors/spec/controllers/palette_sets_controller_spec.rb
	colors/spec/factories/palette_set.rb