Basic tests for some website importers

Hello,

I have finally had the time to sit down and hack on some unittests for the website importers, they are quite crude but they give some coverage and are something to build on.

They use locally cached versions of the webpages to not slow down testing to much with networking. My thinking is to extend them later with some "slow tests" that can be run to detect if the website have changed enough to make the plugin stop working.

I have used [nose](https://nose.readthedocs.org/en/latest/) to run them, which finds some other tests that's not runnable as unittests so I will probably do some clean-up/renaming to make then usable or skipped.