'**SUMMARY**
The convex hull of a blob is the shape that would result if you snapped a rubber band around
the blob. So if you had the letter "C" as your blob the convex hull would be the letter "O."
This method returns an image where the area of the convex hull is white and the rest of the image
is black. This image is cropped to the size of the blob.
**RETURNS**
Returns a binary SimpleCV image of the convex hull mask, cropped to fit the blob.
**EXAMPLE**
>>> img = Image("lenna")
>>> blobs = img.findBlobs()
>>> blobs[-1].hullMask().show()'

def hullMask(self):

    return self.mHullMask
