Canada refactor sso client

#### What's this PR do?
- Fixes remote users creation for local admins
- Uses `drupal_http_request` instead of curl
- Moves corresponding object variables to class constants
- Replaces Exceptions with silent logging
- Deprecates `CanadaSSOClient->getRemoteUser()`

#### Testing
Canada integration tests are consistent with the change:
![screen shot 2014-11-24 at 10 51 48 pm](https://cloud.githubusercontent.com/assets/672669/5172916/b46bd7d6-742c-11e4-8385-474dd00a35b2.png)