Configuring local mail delivery with mailtrap

sending mail with smtp on port 2525 (default mailtrap)
Implemented notification to posters

Send mail to every posters on a topic except current poster
Fixed text mail displaying html entities

using method found on
http://stackoverflow.com/questions/11756304/rails-escapes-html-in-my-plain-text-mails/11763211#11763211
Fixed link in posters notification template.
Moved tests of sending mail to model

Added test to detect moderation status changes in order to send only one
notification when message is approved (manually or automatically).
Added unicorn to Gemfile in order to use it on deploy
Merge branch 'text_mails'

in order to send clean mail notifications
Merge branch 'notify_users'