Fixing incompatibility with the easy-fancybox plugin

In the latest versions of Shashin and easy-fancybox there is an incompatibility regarding loading the fancybox javascript:
Shashin enqueues the fancybox.js under the handle 'fancybox' and easy-fancybox enqueues it under the name 'jquery-fancybox'. Additionally easy-fancybox dequeues every other fancybox dependency. That alone isn't a problem becuase both javascript files are being loaded but the shashin.js is loaded before easy-fancybox's fancybox.js and therefore shashin.js fails to initialize fancybox, aborts its execution and breaks the whole gallery.

This PR fixes this issue by renaming Shashin's handle to 'jquery-fancybox' and making the dependency on fancybox explicit so that Wordpress can resolve it correctly.