remove broken stop word detection, rely on server side implementation

[mattf]

remove the client side stop word detection and rely on server side implementation

two issues with client side implementation -

1. it was not being called in the v0.1 series (last worked in v0.0.20), effectively didn't work
2. it would return part of the stop word (find(...) + 1)

this simplifies the output post-processing, which moves us toward using standard post-processing tools.

[mattf]

I see some logic involving is_stop in _aggregate_msgs() which can be removed as we are not making it part of postprocessing

@raspawar ptal.

i removed extraneous stop params. the is_stopped is used in streaming.