Setup bower and sass, with gulp for building

Second attempt. You were right before, I left the _components.sass out of the main picnic.sass so the buttons / navbar / table / grid were left out! Double checked and everything and there have been no character changes this time (not sure what happened last time :confused:)

I've added build instructions to the readme for those not familiar with npm / gulp. I've also removed the dist folder from gitignore so the built css will be checked in for those who don't want to build it themselves.

As before (if you didn't already anyway) you'll need to register the bower component if you accept this PR