Remove gi and giv aliases

Often mistyping things like `gi tst` causes `gi` alias to trigger the install of
the `tst` gem. This is quite annoying and too close to `git` command which we
run much more often than `gem install`. With bundler we should almost never run
`gem install`.
Improve zsh history

* "to the $HISTFILE incrementally (as soon as they are entered), rather than
  waiting until the shell exits"
* replace any duplicate in the history, not just the previous duplicate: allows
  for a cleaner history
* `.zhistory` is more idiomatic than `.zsh_history`
Add syntax highliting for slim via vim-slim

We are using slim more and more on projects.
Remove RSpec -- profile option

* This option adds a lot of noise to test output
* Extra noise often means scrolling
* The profile includes red, which makes me think tests fail
* Profiling isn't useful when running one or a few tests
* I'm usually not in the mindset of profile tests, so I ignore it
Personal files take precedence over stock files

* First directory listed in .rcrc takes precedence
* We want local config to override general config
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Fix out of date README on rake, rspec commands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 %
Disable zsh correction of command arguments
Add local gitconfig
Don't use zsh vim mode
Add homebrew bin & sbin to PATH
Add some packages to Brewfile
Add git aliases for diff and diff --cached
Add alias to generate ctags for Ruby projects