Added Twitter widget dark theme (https://twitter.com/settings/widgets/new).

Checkout use example: http://augustin-riedinger.fr (in the footer).

Thanks for awesome repo!

Augustin Riedinger
Merge pull request #21 from aug-riedinger/master

Added Twitter widget dark theme
Switch domain from `octocard.info` to `octocard.in`
Merge branch 'master' of https://github.com/zmmbreeze/octocard
Added update code example
Updated README.md