Problem: Having a source file named zyre.c and it's header zyre_api.h is
inconsistent.
Solution:
   * move zyre.h to zyre_include.h
   * move zyre_api.h to zyre.h
   * include zyre_library in zyre.h
Merge pull request #278 from sappo/master

Problem: Having a source file named zyre.c and it's header zyre_api.h is