Merge pull request #25 from jcf/dotfiles-javascript

Add Node and NPM installation script
Silence output from dotfiles-autoupdate
Silence output from installing Heroku plugins
Silence output from installing packages
Ignore errors when Emacs is already installed
Stop setting up autoupdate during dotfiles-install
Stop installing Powerline
Update Ruby versions
Fix Vim setup script
Update cabal during dotfiles-update