Add testing of saved rules

[brashrebel]

Creating, saving and editing the redirect rules is super easy with this plugin. It's what I like most about it. But it could be even more helpful to users if it helped prevent them from making mistakes and confirmed that the authored rules have the desired affect.

I think it would be really cool to add some simple feature which runs a test on each rule and then shows the user some visual indication of success or failure. We could make a request in the background to the URL and make sure there is no redirect loop or conflicting rule and then show a nice green light or check mark or whatever.

Not sure if this should be manually triggered for each rule. Maybe. Maybe a function should also be present for bulk testing the rules.