Implement more embed code
Supported Media Files:
- Youtube
- Vimeo
- Instagram
- Flickr
- Slidershare
- Speakerdeck

close #26
Merge pull request #46 from ChrisBr/implement_more_embed_code

Implement more embed code
* Update devise to latest version
* use letter_opener for mails in development
* bring back the flash
* fix redirect loop for logging in
* move all mailer/devise settings to config/config.yml
Use user_registration_path instead of hardcoded /accounts for deployments into sub-directories...