Refactoring

I started working on adding a grace period feature but realized I was jak shaving. As I threw away that incomplete work I didn't also want to just dump what small fixes I had done. So here goes.

- Only process Jekyll site when Guard actually [wants us to do work](https://github.com/guard/guard/wiki/Create-a-guard).
- Fixed some coding style as reported by rubocop.
- Save Jekyll site to be reused between processes.
- Styled messages similar to most other guard plugins.
- Also run Jekyll process when files has additions, modifications and removals.

Sorry for the big, consolidated commit. Hope you find something agreeable.