'**SUMMARY**
This method returns the longest dimension of the feature (i.e max(width,height)).
**RETURNS**
A floating point length value.
**EXAMPLE**
>>> img = Image("OWS.jpg")
>>> blobs = img.findBlobs(128)
>>> for b in blobs:
>>>    if b.length() > 200:
>>>       print "OH MY! - WHAT A BIG FEATURE YOU HAVE!"
>>>       print "---I bet you say that to all the features."
**TODO**
Should this be sqrt(x*x+y*y)?'

def length(self):

    return float(np.max([self.width(), self.height()]))
