Update tests

[parmegv]

In this Travis build a lot of tests fail, and it seems they do because they are outdated.

For instance, one of them tries to import a Crawler class that does not exist from crawler.py. Now there are CrawlerBase, CrawlerWebFP and CrawlerMultitab.

[mjuarezm]

Thanks, @parmegv! I'll go over the tests and clean them. We also need to write new ones.