'**SUMMARY**
Returns a 2d numpy array of the x,y coordinates of each feature.  This
is particularly useful if you want to use Scipy\'s Spatial Distance module
**RETURNS**
A numpy array of all the positions in the featureset.
**EXAMPLE**
>>> img = Image("lenna")
>>> feats = img.findBlobs()
>>> xs = feats.coordinates()
>>> print xs'

def coordinates(self):

    return np.array([[f.x, f.y] for f in self])
