Set Unix line ending preferences for git

So that git handles the different line ending requirments of Windows and
Unix-esque systems automatically.
Add some common git aliases
Modify bashrc for my rbenv + bundler setup

One key note here - this setup assumes that bundler will be used
to save gems locally to each project. Unless you want to install
gems user-wide (in which case, why not just use gem install) you
should run bundle install --path <local gem folder>
Tweak rbenv/bundler setup