json2pb.cc: make JSON->pb float conversions less picky

json2pb.py might format floats without decimal point, which
will trip parsing in json2pb.cc
hal/cython: BufRing becomes MultiframeRing
gitignire src/hal/cython/machinekit/*.c

only explicitly add those with -f
hal/cython: add ready() method to MultiframeRing
hal/cython: expose StreamRing

byte-oriented ringbuffer - like a pipe
tutorial/protobuf: polyline message example

this shows how to:

- generate a message in Python, and serialize to wire format, JSON and the
standard Protobuf Text Format

- parse a message in C++ from wire format, JSON or Protobuf Text Format

- parse a message in C from wire format, using nanopb - this is realtime-
compatible
tutotial/zeromq: publish/subscribe examples

run the basic demo as:
window 1:  python publish-basic.py foo bar baz
window 2:  python subscribe-basic foo

run the demo with subscriber notificaton:
window 1:  python publish-xpub.py foo bar baz
window 2:  python subscribe-xsub.py foo

no argument on subscribe-*py will subscribe to all topics.
tutorial/zeromq: request/reply examples

shows proper routing.
window 1: python server-reply.py
window 2..n: python client-request.py
tutorial/ringbuffers: basic Python single-frame demo

realtime needs to be running.
tutorial/ringbuffers: multiframe ring demo

realtime needs to be running.
tutorial/ringbuffers: stream  ring demo

realtime needs to be running.