Merge pull request #17 from guardian/libsass

Swap out RubySass for LibSass
Add Embedding instructions to README
Use 4 space indents everywhere on Gruntfile.js
Alphabetise loadNPMTasks
Remove snapPathLocal
Add grunt-contrib-connect and change all double quotes to singles
Half add local snap url
Output local url
Use sass comments rather than css comments to reduce output size
Watch source folder for changes
Use Jit-Grunt
Merge pull request #18 from guardian/general-fixins

Allow for local development, update readme, Jit-Grunt, general clean-up
Add .gitkeep file
Merge branch 'master' into comment-au