[PROPOSAL] make .on() respect .decode pipe.

[houd1ni]

Related: #30

I'm thinking of

• making .on() handlers take decoded data
• and of making new type of handlers - native ones, that would be called .onNative().

[houd1ni]

Maybe better to use .on() only, but call them with two arguments: first is fully cooked data message, if available, and the second is a native event object.