Fix for topic filter not working in ie8

Relates to https://www.pivotaltracker.com/story/show/68808478
Previously the topic filter didn't refresh the results in IE8. Wrapping
the HmrcContacts in an anon function and namespacing GOVUK to window
fixes this.
Merge pull request #118 from alphagov/fix-for-ie8-fiter-not-working

Fix for topic filter not working in ie8

https://www.pivotaltracker.com/story/show/68808478