Fixes timeout in bundle install

When we try to make a bundle install
The command crashed when trying to download the gem 'twitter-bootstrap-rails "

Gemfile in the master branch of prezento was

gem 'twitter-bootstrap-rails',: git => 'git: //github.com/seyhunak/twitter-bootstrap-rails.git',: ref => '95de3b0'

And we received timeout.

I changed to:

gem 'twitter-bootstrap-rails',: git => 'https://github.com/seyhunak/twitter-bootstrap-rails.git',: ref => '95de3b0'

And it worked correctly.