Merge pull request #61 from ospreys-2014/model_migration

Model migration
modified the link_to for genres
Adds image_url field to genres
Adds new genres to seed file
Adds images to all genres. Modifies user1 to have password 1
Cleans up grid for genres. Still needs to resize all images to uniform size
Merge pull request #62 from ospreys-2014/front_end

Front end
basic commenting
comments work now
Merge pull request #63 from ospreys-2014/artist_profile

Artist profile
ratings placeholder add to artist show page
create nested routes for rating users (artists really)
create accessible object for the artist and accessible object for the current user who is logged in
add partial for a form that allows rating
removed unnecessary index route for ratings
update create to permit the params
add rating form to rate an artist
assigned params for artist_id to a variable for readability
removed empty method from user model
add methods to average the ratings for any given entity (ie, artist, review, comment)