Include the base_path when building document URLs

At the moment, the URL that we link to from the document title in email
alerts only include the Plek `website_root`.

This changes the `EmailAlert` model so that the value of the `base_path`
document attribute is appended to `website_root`. 

This means that users will be linked to the full content item on GOV.UK, 
rather than the homepage.
Merge pull request #26 from alphagov/include_base_path_in_document_links

Include the base_path when building document URLs
Use correct redis configuration in LockHandler

Previously the LockHandler was just attempting to connect to redis with
the default config, which works when redis is running locally.  In
production, redis is not running locally, so we need to pass the proper
configuration in.
Merge pull request #27 from alphagov/use-redis-config-in-lock-handler

Use correct redis configuration in LockHandler