Segmenter is memory hungry

[bitsofbits]

The segmenter is unnecessarily memory hungry. This became an issue during the rewrite to improve the core of the segmenter, which generated a lot more noise segments, and in turn caused crashes due to insufficient instance memory. Fix should be straightforward and consists of two parts.

• Filter out noise segments.
• Use Cogrouping of segments and messages rather than passing segments in as a side input