Updated WikiDescription widget to use Wikipedia instead of dbpedia

As nice as dbpedia's API is, they've had some flaky up and downtime, and don't support requests over https. Wikipedia does (and is quite a bit more stable), so this widget uses that API instead. 

Eventually, it would be nice to write and deploy a KBase service to handle this, which would give us some caching as well, but this is a decent in-between step.