message: Update README.md
  add hit count
diff: @@ -88,3 +88,5 @@ The list of PCM environment variables is located [here](https://github.com/opcm/
  Custom compilation options
  --------------------------------------------------------------------------------
  The list of custom compilation options is located [here](https://github.com/opcm/pcm/blob/master/CUSTOM-COMPILE-OPTIONS.md)
  +
  +[![HitCount](http://hits.dwyl.com/opcm/pcm.svg)](http://hits.dwyl.com/opcm/pcm)
  