Die flash, die !

This is a big merge request, I've replaced tagcloud.swf by tagcanvas.js.
No external plugin needed, faster and tested with firefox, chromium and android 4.2.2 browser. It should also work with MSIE >= 9, but I've not tested.

It also integrates this commit from pull request #3:
https://github.com/guori12321/octopress-cumulus/commit/0af2339ba1f2ce574a8a17d706e56b3aee6835a1