Add unit test for noremap.
Make map and noremap commands affect OMAP.

- in Vim, map and noremap commands affect normal,
  visual, and operator-pending mode
- see :help noremap in vim
- added the lately introduced OMAP to the list of
  KeyMaps changed by map and noremap
Merge pull request #397 from wawe/map-affects-operator-pending-mode

Map affects operator pending mode