update gitconfig
Merge branch 'master' of https://github.com/ay65535/dotfiles

# By ay65535 (22) and Yan Pritzker (1)
* 'master' of https://github.com/ay65535/dotfiles: (23 commits)
  Update install.sh
  Update gitconfig source tree path
  Update prezto
  競合を解決
  色々修正
  カスタムprompt preztoへ
  Disable alias that already defined in prezto
  merge gitconfig, gitignore from dotfiles, yadr, dotfiles_mathiasbynens
  Update gitconfig
  Change zsh theme
  Edit Rakefile
  Enable ruby prezto module
  いらないoverrideはコメントアウト
  Customize prompt
  Update README.md
  zpreztorc (override) をpreztoと統合． install.shを変更しDropbox内にcloneするようにした．
  Update prezto, gitconfig was auto-modified by SourceTree.app
  Change prezto repo to ay65535/prezto
  Update README.md
  Update README.md
  ...