Update text.scss to take advantage of SASS
Update text.scss to take advantage of SASS

As part of the frontend toolkit work that @intranation has done, we
should be merging this in and getting as much of our code using it as we
can.

This change simplifies a lot of the code that we have for article text
by structuring it to use sass blocks, helpers, and our own mixin
methods.

tadast/static,robinwhittleton/static,robinwhittleton/static,kalleth/static,tadast/static,tadast/static,kalleth/static,alphagov/static,alphagov/static,tadast/static,robinwhittleton/static,robinwhittleton/static,alphagov/static,kalleth/static,kalleth/static