working contouring
createVideoWriter should not accept Monochrome images

* http://docs.opencv.org/modules/highgui/doc/reading_and_writing_images_and_video.html#videowriter-videowriter
* the error in https://gist.github.com/aavogt/59da0e98bfeaac0c9f1b
  becomes a type error with this change
Merge pull request #2 from aavogt/master

working functions for contours & restrict createVideoWriter