Added OmniAuth support for authentication.
Added background worker for processing character assocations upon authentication from battle.net.
Added local image retrieval for character avatars via Paperclip (closes #70).
Cleaned up characters.js.coffee (removed api_key functionality).
Fixed issues with empty datatables for character, character_history, and standing.
Improved ability.rb model to allow :sync, Character action for owned characters.
Cleaned up characters view (removed deprecated files).
Fixed 404 error for image retrieval in Character model.
Removed character.portrait string field and replaced with Paperclip asset.
Cleaned up _spec files with deprecated character.portrait field.