DO NOT MERGE!

Just opening this pull request for discussion.
At the moment it just implements the /ignore and /unignore
commands, not the actual filtering. It's also missing tests.
My plan is to add the filter at the Core::Connection layer. 
Wondering if this should hold until the Mojo::Redis2 port is
done tho, as it's a little redis-heavy.

The first question tho is if this is a good idea at all. What do you
think, @jhtorsen?