Tables should use strings

During the performance analysis of spotlight we realised that ever
request spent a lot of CPU and memory rendering tables. It was shown to
be the use of the 'DOM' that caused these performance issues. Switching
the rendering to assemble strings and then parse them in one go has
reduced the mean response time, on local loadtest, by a factor of 5.

The tests have been modified to consider the output of render rather
than messing around with the intermediary functions.
Force Modernizr into thinking its on a tablet

In order for this test to run on a desktop browser we need to force
Modernizr.touch to be true and reset it when the test is done.
Merge pull request #621 from alphagov/refactor/table-rendering

Refactor/table rendering