[holman_script] Start on a smarter install process

Run a script that installs from Homebrew. Eventually this would
be great to nuke the rake dependency and do it all in shell. I
kind of hate all of this... this should be more modular and
cleaner. Always something to do!

This also closes #31.
[holman_script] Added a check so the install script does not use homebrew on *nixy systems
[holman_script] short explanation: bootstrap script broken

know-it-all explanation:
  The test command [ needs a trailing space to be recognized.
  In #!/bin/sh environment, '=' has to be used with the test command.
  ] needs a leading space to be recognized as the last argument of the test command.
[holman_script] Move homebrew to its own thing
[holman_script] Move 'rake install' to script/bootstrap
[holman_script] Remove OUTPUT related stuff.
[holman_script] Update input styling
[holman_script] Run `dot`
[holman_script] Nicer dependency output
[holman_script] Bootstrap the gitconfig.symlink.example file with author name and email.
[holman_script] Fix #76
[holman_script] Use bash not zsh or sh.
[holman_script] Update bootstrap

Use env(1) to locate shell binary (see http://en.wikipedia.org/wiki/Shebang_%28Unix%29#Portability).
[holman_script] Update gitconfig to use osxkeychain for OSX and cache for other systems
[holman_script] Auto run all install.sh scripts

This adds a ``script/install`` that iteratively runs all ``install.sh``
scripts located in the dotfiles directory. Solves @holman's request from
commit f697ba7
[holman_script] Grammar
[holman_script] Better `cd` in installer

With `cd "$(dirname $)"/..` it works bad, because `$(dirname $)` will return `.` so it implies that to correctly works, you have to be in the `script` directory, otherwise if you're e.g. in `$HOME/.dotfiles` you'll go in `$HOME` and then look for all `install.sh`, which may not be what you intended to do.

Using `$(dirname $0)` instead ensure that you'll go one level higher than the `install` script.
Add 'script/' from commit '974fdd50ac735dd05fead3f629dd1e444f0eb138'

git-subtree-dir: script
git-subtree-mainline: f545f9fb921f835b0561b657da142dedacd7e494
git-subtree-split: 974fdd50ac735dd05fead3f629dd1e444f0eb138