Problem: need a basic plug-in model for streams

Solution: use an actor API with async message flow. Implemented by the
mlm_stream_simple actor. See STREAM.md for protocol details.
Problem: need continuous integration tests

Solution: make Travis CI integration
Problem: Travis script does not build Zyre so configure fails

Solution: we will use Zyre later; rather than remove this from the configure
script I've added it into .travis.yml.
Added missing include of labs/zbits.h
Fixed use of include files
Problem client 'attach' and 'subscribe' are clumsy names

Solution: use 'produce' and 'consume', these work better.
Problem: Document whitespace settings
Merge pull request #12 from hintjens/master

Problem: need a basic plug-in model for streams
Problem: generated code is too slow

It takes about 3 seconds to send 100K messages from client to server
to client, i.e. 200K messages in total, or 65K / second.

Solution: start by rewriting message codec to reduce use of heap
memory.
Merge pull request #14 from bripkens/editorconfig

Problem: Document whitespace settings
Travis failure due to outstanding PR in CZMQ; merging anyway.
Merge pull request #15 from hintjens/master

Problem: generated code is too slow
Travis failure due to outstanding PR in CZMQ; merging anyway.
Problem: Reference to Malamute image is broken
Merge pull request #16 from bripkens/fix-readme

Problem: Reference to Malamute image is broken
Fix README typo
Merge pull request #17 from trevorbernard/master

Fix README typo