Replaced the merge code with something less efficient but easier to
grok.

New stream impl that does not read the data that will be used to create
and index used in new merge code.

* Ensure streams is a know iterable type (deque)
* Make sure to reuse a stream in the case of a bad packet group. This was
  done with an exception so it was handled the same way as the other 2
  major cases.

bug fix, we were doing streams.remove(stream) inside a "for stream in streams:" which gave incorrect results

Reimpl stream functions as classes.