Include gitconfig.local file for personal changes

* assumes same directory existance
* allows for easier addition of personal configs
Include local aliases file

* `.aliases.local` should be used to add personal aliases
Source ~/.zshrc.local if it exists

Follows the pattern of:

* ~/.aliases.local in ce7ad49
* ~/.gitconfig.local in 8e141fe
* ~/.vimrc.local in a666267

Use consistent:

* `source`ing style.
* commenting style.

I am using ~/.zshrc.local as a home for `eval "$(rbenv init -)"`.
Remove "DO NOT EDIT BELOW THIS LINE" convention

It has been superceded by a `.local` suffix convention.
Git push to current, not upstream

The primary use case for me is to `git push staging` and `git push
production` from the master branch using our typical git workflow:

https://github.com/thoughtbot/guides/tree/master/protocol#deploy
Make the migrate alias faster

This was loading up the environment four times when it really only needs
to happen twice.
Remove unused vim plugins

* haml, html and markdown highlight still work without these plugins
* treetop and textile are likely very situational
* unsure if anyone is using greplace
Remove old ignores

* sass gets compiled to `tmp/sass-cache` with Rails
* vendor/bundle_gems seems like an arbitrary vendor directory
* vim/.netrwhist is for a plugin we no longer use
List local files available to override
fix relative .aliases.local path
Add syntax highlighting to certain file types

* Syntax highlight `Appraisals` as Ruby. Used especially for our open
  source libraries.
* Syntax highlight rackup (`config.ru`) files as Ruby. Used in all our
  Ruby web apps. Rails apps are rarely touched but some of the Sinatra
  and Middleman apps are occasionally edited.
* Syntax highlight JSON files as JavaScript. Used in our Trail Map.
Remove redundant syntax highlighting

Newer versions of vim (such as 7.3.923) syntax highlight Rackup and JSON
files correctly. In the interest of keeping the dotfiles slim and our
machines up-to-date, I think the solution is to remove these from
dotfiles and install a newer version of vim in thoughtbot/laptop:

https://github.com/thoughtbot/laptop/pull/118
Adds local configuration file for vim bundles
Allow for a local tmux.config file
Add rspec config file

* Colorize output
* Run tests in random order
* Profile 5 (default of 10 is too noisy)
Don't cache CtrlP results when using ag

It gets very annoying to manually force CtrlP to re-index every time I
add a new file. Since ag is so fast, we can turn off caching when it
powers CtrlP without any noticeable impact on search speed.
Allow backspacing over everything in insert mode

The previous setting frequently slowed my ability to edit.
Add Git credentials.
Initialise rbenv on startup.
Add Homebrew directory to PATH.