Add subtitle to site header

Added the subtitle as configured in _config.yml to the site header,
since it wasn't being used anywhere else and some might want it
back.

Subtitle follows the main title, styled as small.muted

Users can disable the subtitle by not setting one in _config.yml
or editing the _includes/custom/header.html file
Adding support for Twitter Widget @eToThePiIPower

  - Update README with instructions for using Twitter Widget
  - Restructure Oscailte's social yml configs
  - Rework existing code to work with new config.yml structure
Add support for Octopress {% img %} tag

  - Update README and its Update info
  - Closes #45
Update language and typos
Fix anchors
Merge pull request #48 from coogie/develop

Add support for Twitter Widget and Liquid img tag
Make sure users get Master branch
Merge pull request #49 from coogie/develop

Make sure users get Master branch
Merge remote-tracking branch 'upstream/master'