Peter M. Groen / redox

subscribe/psubscribe/unsubscribe/punsubscribe methods that keep track of
subscribed topics to make sure we don't ask hiredis for bad things. It
appears all crashes are eliminated, though no stress testing has been
done.

subscribe/unsubscribe/publish with proper and working callbacks. Guard
added that throws an exception if a non-pubsub command is issued after a
subscribe.

Also removed all std:: prefixes from redox.cpp. Just made the decision
for "using namespace std" there for readability. Not a header, of
course.

Also added another async watcher for breaking the loop, since ev_break
doesn't actually do anything when called outside of an ev_run callback.