Moved third party package to the bottom of the imports
Defined setter methods for header fields
Dropped repeated fields support
ripped out nasty repeated fields
Removed CZMQ dependency from zproto

Problem: cannot run "make install" without CZMQ, and cannot make CZMQ
without installing zproto.

Solution: remove C link/compile from Makefile; as zproto depends on
multiple languages, each will have its own test process. Also, in
makefile, generate example code in all languages.

Fixes #93