General cleanup

- Updated [Normalize](https://github.com/necolas/normalize.css) to 3.0.1
- Removed unused compiled CSS version of Normalize (it’s being brought in via a Sass partial)
- Combined Google Fonts `link` tag into one, for fewer HTTP requests
- Stripped comments from Middleman configuration, `.gitignore` and Gemfile
- Swapped single prime marks in favor of double prime marks
- Renamed `LICENSE.txt` to `LICENSE.md` to be consistent with `README.md` and Bourbon suite