Merge branch 'remove-implicit-relative-imports'

This fixes a:

  pycomedi ImportError: No module named chanspec

error reported by Lukas <dwisuu@gmail.com> [1].

[1]: id:51e4fc1f-b367-4a69-a59b-39adf383a961@googlegroups.com
     https://groups.google.com/forum/#!topic/comedi_list/5qo3u_Qjx2Q

* remove-implicit-relative-imports:
  Use generators, now that Cython supports them
  Don't use: from pycomedi cimport module as _module
  Use relative imports (or absolute imports for cimport)

diff --cc pycomedi/constant.pyx
Simple merge