Add StackShare icon to README
Update about.twig
Fix AboutPageTest by adding Charl's Twitter URL

Also refactored a little to allow for different domains without being
too silly
Set application up for a Dokku deployment

BREAKING CHANGE: the file formerly known as `.env` has been renamed to
`.config`. The current `.env` file IS kept in source control and has
references to the correct buildpack to use on Dokku / Heroku.

Other changes:

- The RoboFile's asset task now copies fonts over

- The unauth'd header now points to /signin instead of /signin.php

- Various composer packages were moved into the main requirements object
  instead of the -dev one.

- Extra deployment-related settings were added to the composer.json file
Merge Dokku changes into master branch