Remove functions wrapping Zeus

Project should be moving over to spring, as this is the 'blessed'
approach and is part of suspenders. Leaving these functions around adds
yet another layer of indirection to consider when trying to run these
commands:

* function wrapper
* binstub
* rbenv shim
* actual binary
Remove trailing whitespace in gitmessage
Automatically prune remote branches when fetching

* Removes the need to occasionally run `git remote prune`.
* Remove branches when fetching instead of deleting other branches.

https://trello.com/c/ePlghTll/249-configure-git-to-prune-on-fetch
Add vim-mkdir

`:e some/non_existent_directory/new_file.txt` usually errors out because
the directory does not exist, but with `vim-mkdir` the non-existent
directory will be created automatically.
Enable shiftround

With `shiftround` enabled, using `>>` will indent the line to the next
multiple of `shiftwidth`. This is useful when you are indenting
improperly indented code.
Run commands interactively from vim

This allows us to do things like:

    <Leader>r migrate
Fix out of date README on rake, rspec commands

`rake` and `rspec` commands that wrapped `zeus` were removed in 00dbd15.
Show only basename and git branch in prompt

* Switch order from "[git branch][pathname]" to "basename git branch %".
* Remove noisy brackets.

Example old:

    [master][~/dev/thoughtbot/dotfiles]

Example new:

    dotfiles dc-prompt %
Merge remote-tracking branch 'upstream/master'

Conflicts:
	zsh/functions/rspec