Remove the multivariate testing code; the test is done.

This reverts commit b9f00e83d8082fea2496cfde73933296ef40eafd, reversing
changes made to d7b6c26d99de804abd621d99ecea4c882a2e4c17.

Conflicts:
	Gemfile
	Gemfile.lock
Remove contact page assets from pre-compilation
bump rake, multi_json back up to recent versions
Merge pull request #116 from alphagov/remove-contact-page-multivariate-test

Remove the multivariate testing code