Remove reattach-to-user-namespace

This is Mac OS X-specific. Including this line in the dotfiles causes
`tmux` and `tmux new -s new-session` to break with `[exited]`.

I personally don't do copy-pasteable work inside tmux anymore.

I'm sure this is valuable to some of the thoughtbot vim users but I'm
thinking it better belongs above `DO NOT EDIT BELOW THIS LINE` as custom
configuration for those users.
Add user details.
Add easier navigation between split-windows.
Use bundle to execute rspec.
Add the Solarized colours bundle.
Change colour scheme to Solarized.
Add heroku to the path.
Add easy swapping for Rails projects.
Add an alias for bundle exec.
Install TMUX Powerline.
Add an alias for TMUX.
Hide the status bar.
Replace thoughtbot scripts with Matt's.
Always show the tab bar.
Add an 80-character limit.
Update prompt for powerline.
Load RVM at startup.
Add a cap alias.
Add a branch alias.
Remove alias for branch.