Support for OpenCV 3 and PyVision3

There is now an 'opencv3' branch in PyVision that works well with both OpenCV 2.4.* and OpenCV 3. Eventually this will probably get merged into master. Note that the branch will break backwards compatibility with previous versions of pyvision and some functionality will be lost. I think the SVM classifiers now longer work. In the future machine pyvision will rely more on scikit-learn for machine learning and scikit-image for image processing. Both these libraries are now stable and easy to use and offer new and complementary functions beyond what is provided by OpenCV.

As an alternative Steve O'Hara, who was a major contributor to the original PyVision, has created a reboot of the library called PyVision3. This reboot keeps many of the best aspects of PyVision but no longer focuses on wrapping other packages such as OpenCV.