Fixes for deploying to heroku, changing div to iframe, sending application emails, adding subdomains to viewers

- fixed jquery-ui error message: they removed jquery-ui from jquery-rails gem, so I've added this jquery-ui-rails gem to Gemfile, and jquery.ui.all to application.js, also added a dummy jquery-ui.js for active_admin (until it is fixed).
Also encountered another error when running heroku and moved bootstrap-sass gem from assets group to fix it.
- changed video quiestionnaire to iframe from div
- Added link to sending applications to viewers#edit page, next to 'show' | 'back'. User can enter emails, change from address, set subject and edit html/text bodies. Not sure how you would want to separate them, so keep it simple for now. It seems sending ok, I get messages to inbox, not spam folder on GMail.com and Apple's Mail. To change user-editable template, edit views/application_mailer/template.*.erb. Non-editable parts add to views/application_mailer/new_application.*.erb
- added short links to viewers via subdomains. In order to place short link use ```viewer_short_url(viewer)```, it will generate correct link with subdomain.

UPDATE:
- I've replaced mandrill SMTP settings with direct api usage, therefore instead of ActionMailer, I use plain ruby class for sending emails and removed templates. You can change templates in Application model, and/or make use of Mandrill templates. You will need to set Mandrill api key in MANDRILL_API_KEY environment variable for it to work.
- moved sending application into a modal