Allow regex to be passed via query string

First of all, thanks for this amazing tool!

I'm about to launch something to do with RegEx (I'll give you a preview of it soon - should be this week sometime) and being able to pass in a RegEx via query string (or some sort of API if not this) would be very, VERY handy.

I thought about the need to possibly sanitize the input, but I'm not entirely sure this is necessary.