Zaahir/spice test with regex

Allow for a testing the Spice's `call` against a regex instead of just a string comparison. This will make it much easier to test certain, dynamic Spices, such as those that are time dependent.

I guess we haven't previously needed this functionality but it seemed like it might be necessary to test the new Flights IA (https://github.com/duckduckgo/zeroclickinfo-spice/pull/1271)

//cc @mwmiller @jagtalon