Allow columns to be flipped for RTL content

For right to left locales the reading edge is on the other side of the
page. In reality this means that the most important content should be
against the right side of the page and the columns should be flipped.
This makes it easy to have all the columns on the page flipped by
adding a wrapping class to the page.
Merge pull request #507 from alphagov/rtl-grids

Allow columns to be flipped for RTL content
Add Universal Analytics snippet

In order to migrate to Universal Analytics we need to run the old and
new code side by side for a while. Add the snippet and UA bootstrap
code.
Merge pull request #508 from alphagov/universal-analytics-snippet

Add Universal Analytics snippet