Add byte_limit to Emitter

[alexanderdean]

This is the same as we do in the Kinesis apps, where it works well.

[chuwy]

I think this should be changed to "Add byte_limit to Emitter". I started with refactoring of Emitter, adding new Buffer object that handles all these three limits, event list and related things, but this refactoring became too big and overengineered.

Instead:

1. we always had event-limit (buffer_size parameter in Emitter)
2. we added time-limit as per Add ability to automatically send all events in buffer at a regular time interval #114;
3. which means we just need to add byte_limit. And I think this byte limit should be for python-object-in-memory rather than json-going-to-be-sent-over-network, because stringifying objects just to calculate JSON size would be very ineffective.

Alexander Dean (@alexanderdean) what do you think?

[alexanderdean]

Fine by me - Yali (@yalisassoon)?

[yalisassoon]

Good by me!

[chuwy]

Cool. Renamed issue