adding filter. using sift
refactoring events on main brokr object.

All internals is now emitted with underscore as first char.
Forced topics (aka. meta topics, aka. broadcasts, aka starts with #)
is now implemented and used for filters. Filters now works.
When creating a filter, you automatically subscribe to it's broadcast
regular pubsub's are emitted by topic name on brokr object.

So, recap.
"_error", "_subscription", "_connection" are brokr internals events
"#my-broadcast", "#my-filter", "#lol" are broadcast message topics
"notifications", "my.topic.name" are regular pubsub topic names