ktensor.normalize error when sorting

[dmdunla]

There is a bug in the following code in ktensor.normalize():

if sort:
            if self.ncomponents > 1:
                # indices of srting in descending order
                p = np.argsort(self.weights)[::-1]
                self = self.arrange(permutation=p)

ktensor.arrange does not return a ktensor. When ktensor.normalize(sort=True) is called, None is returned due to the last line. The code self = should be removed in the last line above.

The documentation for arrange should change as well to reflect this, as ktensor.arrange documentation states that it returns a pyttb.ktensor.