Update homebrew install script url

Home homebrew install Gist (https://raw.github.com/gist/323731) has been removed. New link (https://raw.github.com/mxcl/homebrew/go) taken from official website (http://mxcl.github.com/homebrew/)
Update link to @sorin-ionescu Oh My Zsh

Oh My Zsh fork now renamed to Prezto
Merge pull request #129 from JeanMertz/patch-2

Update link to @sorin-ionescu Oh My Zsh
Merge pull request #127 from JeanMertz/patch-1

Update homebrew install script url
Merge branch 'master' of https://github.com/luxerama/dotfiles

* 'master' of https://github.com/luxerama/dotfiles:
  adding vim directory in custom to gitignore
  enabling theme changes when using prezto through zsh before