The base HTML structure enables the responsiveness for the
website. In addition to the primary base template, the generic
page and form templates are also modernized.
Authors: Sarah Conway <sarah.conway@crunchydata.com> and me
We don't want to use django style headlines and margins in the preview,
we want something that looks a bit more like the main site. It's not
going to be exact (e.g. the colors will still be wrong), but it will
be a lot closer than without this.
This will do simple html detection based on trivial regexps. If HTML is found,
it will replace it with HTML_REMOVED and also show a warning (in red color,
no less) that this is not permitted.
The actual filtering is still done server-side later, so the fact that these
regexps are trickable if you really want to doesn't matter...
Fixes#164
