More efficient ruleset checking
Currently every request from the browser occurs an overhead that is O(N) where N is the number of rules (or rulesets with match_rules).
This is not good enough, especially if we intend to include all the rules people are submitting.
O(1) lookups should be possible. One way is a dictionary of target domains, with lookups looking something like this:
If the request is for content at blah.thing.com, we look up
.thing.com, thing..com, blah.thing.*
in the dictionary. For the time being, rulesets should be able to signal what domains they target in at least that level of specificity
Eg, Google.xml targets:
BUT, if we ever had to worry about .google. this wouldn't be enough...