Runs UK and Canada tests on international subdomain.

#### What's this PR do?
- Makes UK and Canada integration tests run on international domain so `dosomething_settings_get_affiliate_country_code()` would return right value inside the tests
- Fixes an error in `bin/test` script with url detection
- Makes `casper.drush` take into account an affiliate currently executing test at
  ![image](https://cloud.githubusercontent.com/assets/672669/5051158/a5426c80-6c3d-11e4-8452-b5ad929dc66c.png)

#### Any background context you want to provide?
Now running tests requires an amend to of `/etc/hosts` file that assigns intl hosts to 127.0.0.1, e.g. `127.0.0.1 dev.canada.dosomething.org`.
This will be fixed in the new box build.
Could you add a quick comment here to explain what this does? Took me a few seconds to understand why Drush needed to being passed the URL, and that the variable was coming from the global var set in other Casper file.