Don't use key called 'class' in report-a-problem.js

In IE8 'class' is a reserved keyword. (??!!!)
Wrap analytics scripts in closure scopes

Apart from being a good idea anyway, IE8 has a strange
habit of destroying window.x if var x is declared in
a script scope. The upshot is that doing:

var GOVUK = GOVUK || {};

will cause window.GOVUK to be deleted at the end of 
the script's execution.
Merge pull request #380 from alphagov/ie8-fixes

Ie8 fixes