Added jekyll-contentblocks to the plugins list
Merge branch 'add_contentblocks' of git://github.com/rustygeldmacher/jekyll into rustygeldmacher-add_contentblocks

* 'add_contentblocks' of git://github.com/rustygeldmacher/jekyll:
  Added jekyll-contentblocks to the plugins list
Update history to reflect merge of #1068.