Added support for Gruntjs to automate the sass compilation task and enabled liverelaod

The idea behind this enhancement is to bring in support for Gruntjs which is commonly available with many libraries and frameworks. Using the grunt server command on the command line, the grunt file shall take any config from the config.rb file and accordingly watch the files for changes to the sass files and automatically compile the gumby.css file on the fly. I have also added the grunt connect module which will start a quick static server at localhost:9001. It can also be a good starting point for nodejs developers to get a headstart with Gumby.