Enhanced project part handling via Gulp

[deksden]

Add some usefull processing for different parts of project:

• JS: lint, concat, minify, uglify;
• css: unCSS for bootstrap, concat, minify;
• vendor CSS/JS in original, not minified form;
• reimplement Bloc's features in plain HTML/CSS;
• HTML: validate, minify;

[deksden]

Progress so far: CSS is optimized via UnCSS and Critical. Also minification is set for CSS/HTML/JS.

TODO: lint for JS, validation for HTML/CSS