add twitter, google plus, and facebook sharing
add sharing info to README
add more twitter options
add google plus options
add default values to social media parameters
Fix 'true'/True oddity

- A bit gross (series of filters) but allows us to use booleans in Python, and
  strings in Javascript
First attempt at fixing twitter
Added working twitter example

- Not 100% sure if it mirrors previous setup, but I think it is close
Corrected Google Plus docs
Forgot to add myself as author
Merge branch 'sharing' of git://github.com/nt3rp/pelican-octopress-theme into nt3rp-sharing

Conflicts:
	templates/_includes/after_footer.html
	templates/article.html