There is a separate branch for the Twitter Bootstrap 3 gem. I understand from this SO question How to install gem from GitHub source? that when installing a gem from github, the url should end in .git
However, when I go to the github page for Twitter Bootstrap 3 gem, the cloning url is exactly the same for Twitter Bootstrap 3 as it is for the master branch (version 2)
https://github.com/seyhunak/twitter-bootstrap-rails.git
How to install Twitter bootstrap 3 gem from github?