Install bundler with specified version instead of latest

The current script pulls down the latest version and does not take into account that the Gem file calls for a specific version, and will not compile properly.  A tweak to the installation of bundler must be done to get the right version:

replace:

gem install --no-rdoc --no-ri bundler

With:

gem install bundler -v "$(grep -A 1 "BUNDLED WITH" ~/raddit/Gemfile.lock | tail -n 1)"