Add coffeescript to ackrc
DRY dotfiles vars in install script. Explain more in comments.
DRY hard linking in dotfile-linker script.
Use git-prompt and get proper Solarized colors for prompt.

This also stops the first line or so of terminal text being white,
and instead being the appropriate color set by Solarized.

Fix #10
Use 256 colors in the terminal.
Stop aliasing git to hub to speedup prompt. Remove git-prompt.sh.

When git was aliased to hub, all programs calling git were calling
hub. When it comes to __git_ps1() used in the prompt, it was being
slowed way down. Since I always use `g` for git, `g` is now aliased
to hub, and `git` is straight-up git. Without hub available, `g` is
aliased to git.

git-prompt is now included from `brew install bash-completion` and
prompt has always been sourcing it if it's there.