Better promotion on twitter

When someone references `http://0hh1.com/` in a tweet, no additional metadata is shown:

![screen shot 2014-11-15 at 8 56 45 pm](https://cloud.githubusercontent.com/assets/121322/5060455/f54946ea-6d0a-11e4-8e3f-17efcb77bbce.png)

If you merge this pull request and [activate Twitter cards for your domain](https://cards-dev.twitter.com/validator) then you should start seeing an icon, additional information, and links to the relevant app store where appropriate:

![screen shot 2014-11-15 at 8 41 01 pm](https://cloud.githubusercontent.com/assets/121322/5060458/207782c8-6d0b-11e4-8bbf-5648c2010677.png)

Cheers,
  Lee :beers:

/cc @mrtnkl