Updates

* 8-bit thumbnails.

  Before: 189 KB (193.931 bytes)
  After:  52,6 KB (53.897 bytes)

* Losslessly compress images.

  Before: 406 KB (416.526 bytes)
  After:  393 KB (403.234 bytes)

* Fix validation errors.

* README.md: new badge.

* Update libraries.

  * normalize.css to v3.0.2.
  * html5shiv v3.7.2
  * respond.js v1.4.2
  * jquery v1.11.1
  * jquery.mousewheel v3.1.12

* Update dependencies.