Rename current file in vim buffer

* Retain relative path.
* Save file.
* Do not keep old file open in buffer.

Usage:

    :e old_file_name.rb
    :Rename new_file_name.rb
Change the 'git commit --amend' alias to 'git ca'
Extract rspec vim bindings to thoughtbot/vim-rspec
Move `.vimrc.local` to the bottom of .vimrc

Having this file be sourced last allows user to
overwrite the configs in `.vimrc` without having to modify it.

* fixed file's path to work with `filereadable`
Increase tmux scrollback lines
Merge branch 'upstream'

Conflicts:
	vimrc