Statamic 1.7.3, gulp task system

- Update Statamic gitignore & htaccess sample
- Add hint, watch & image tasks, remove watch from default
- Smarter js-build process until I come around to add requireJS or
something
Decouple grid modifiers, use Modernizr for flexbox enhancements, Fixed image performance

- Use $grid—modifier__item syntax to prevent code bloat from grid
modifiers
- Merge flex-box enhancements into main recipes with Modernizr
- Fix fixed image recipe paint storms
- Remove a shitload if trailing whitespace