Match rule multiple times

Similar to #15 which allows multiple rules to match (once), I want to be able for one rule to match multiple times.

For example, I have a rule matching `\#([0-9]+)` that should get transformed into issue/PR links. Now if someone writes a message like
> `#1 #2 #3`

then I want my reactbot to post links to all 3 of them, and not only the first.