Updating deps.

Notable changes:

chunky_png:
* Fixed an error n 4-bit resampling code.

fast-stemmer:
* Fixed to work with compilers other than gcc.

fssm:
* Remove deprecation message.
* Fix to work with JRuby.

haml:
* Fix for line numbers reported from exceptions in nested blocks.

kramdown:
* BREAKING CHANGE: Code language is now specified via .language-CODELANG instead of lang='CODELANG'
  * See this page for explanation: http://kramdown.rubyforge.org/news.html