Added npm+gulp assets manager

[michalbundyra]

• Updated Bootstrap and jQuery - linked from CDN servers
• Removed old unused libraries
• Added npm and gulp to build resources for the website
• Used 'asset' view helper from zend-view 2.9.0
• Added section in README.md how to rebuild assets

I've changed following libraries:

• jQuery - served from CDN 🌎
• Bootstrap - served from CDN 🌎
• FontAwesome - served from CDN 🌎
• prismjs - in npm, compiled and minified (in main scripts.js) 📦
• jquery.hoverex - moved to asset as it is, there is no npm version (compiled and minified only for home.js as it's used only on homepage) 📦 🏠
• jquery.isotope - in npm, compiled and minified (only for home.js, used only on homepage) 📦 🏠
• retinajs - seems to be not working properly (also on current website - many 404 in console for files with suffix @2x), removed ❌
• jquery.hoverdir - seems to be unused, removed ❌
• prettyPhoto - seems to be unused, removed ❌
• html5shiv - used for compatibility with IE8 and lower (I think we already decided to not support these browsers anymore), removed ❌
• respond.js - as above, used for IE8 and older, removed ❌

/cc @froschdesign @weierophinney

[froschdesign]

@webimpress 👍 for removing old and unused stuff

Suggestions:

1. I think we can reduce the server requests if we would merge (with Gulp):

   • styles.css and manual.css
   • all scripts for the homepage with scripts.js

2. Add the moment the scripts for the portfolio and the jQuery plugin "hoverex" have a hard dependency to the home(page). When we consider the portfolio as a module, then there is no need to add this dependency. (remove the extra folder)