Comment app and album comments

Signed-off-by: Fernando Rocha <fernandogrd@gmail.com>
Comment serializer to hyperlink

Also removed content_type and object_id from fields

Signed-off-by: Fernando Rocha <fernandogrd@gmail.com>
Merge branch 'comments'

Signed-off-by: Fernando Rocha <fernandogrd@gmail.com>

Conflicts:
	musicstore/musicstore/urls.py