Method changes to SongRepo/AlbumRepo + minor changes.

-Changes to SongRepo:
1. added a youtube key with the youtube link.
2. deleted writer key
3. album_id is now params[:id] instead of params[:album_id] since the :id is the :album_id in params
4. find_by method now returns an array. Each hash of result goes through build method before mapping to the new array.
5. find_all method for now, is not relevant. The corresponding test has also been set to pending.
-Changes to AlbumRepo:
1. When adding, changed back the keys of params from string to symbols
-Minor change in testing:
1. for AlbumRepo, instead of passing in an objet for find_by, passed in {id:1} because the find_by method now takes in params instead of an instance of Album class.
-All tests passed after the changes.