cv2 Support for Haar Cascades

Made changes in the HaarCascade class.

User entered file paths did not work previously.

    h = HaarCascades('/home/face.xml')

this used to get converted into '/usr/local/lib/python2.7/dist-packages/SimpleCV-1.3-py2.7.egg/SimpleCV/Features/HaarCascades//home/face.xml'

This has been resolved.
It now searches in the given path. If it fails then is searches for it in the SimpleCV default directory.

    h = HaarCascade('/home/face.xml') #searches the given path
    h = HaarCascade('face.xml') # searches in the default path if current directory does not have face.xml

Second, 
cv2 support for findHaarFeatures has been added.