Add Gulp dependencies and gulpfile

- Update README with gulp refs
- Ignore sass and gulp work dirs
- Add gulpfile and appropriate dependencies
- Add coffee and gulp-util helpers

Add gulp tasks:

- Minify SASS (.scss) stylesheets
- Parse every .coffee script
- Minify every .js script
- Concat and group minified sources
- Watch for changes

Misc:

- Add jshint and nodemon config
- Refactor public folder layout
- Add new src folder for develop env scripts
- Refactor main jade template with new paths