Styles task rewrite

1. Now uses node-sass instead of ruby-sass, increases speed dramatically.
2. Uses PostCSS postprocessors like autoprefixer and minifier.
3. Full sourcemap support.
Best partices for gulp-watch watch tasks

Followed recommendations on gulp-watch docs for the best way to run watch tasks.
Add clean task to clean folders and start over.
Add/remove settings from config for new tasks
Add revisioning task

Useful for cache busting of changed assets that are saved on browser caches for a long time. This will force the browser to detect the changes and reload them automatically. This prevents errors and quirks for users visiting after a change has been added.
Use run-sequence for better task order

Use new clean task for clean folders before serve task compiles assets. Use run-sequence to guarantee 'clean' is finished before the rest.
Update watchify
Use run-sequence for build and add rev task

Run-sequence guarantees correct order of task running. Run rev task after everything is finished.