Removed Grunt and added Gulp instead

Closes #40, closes #39, closes #31 and closes #30

Changed from using Grunt to using Gulp. This adds support for a couple
of new commands to run and makes everything better (imho). Also
removed the old Jekyll base app and added a newer one taken from my
own Jekyll base.

Also some minor updates for the change into Gulp for the other files,
nothing too major. Yay.