Add low/high range values for random tensor generators

[dmdunla]

Currently, the random tensor generators tenrand and sptenrand generate tensor entries uniformly in the range [0,1].

Suggestion: Consider adding functionality to these methods for generating in other ranges.

Currently in the tutorials, we have the following code to accomplish this:

a = -1
b = 42
np.random.seed(0)
X = ttb.tenrand((2, 4, 3)) * (b - a) + a

And the suggestion is to add the new functionality such that we could call the method as follows (akin to numpy.random.uniform):

X = ttb.tenrand((2, 4, 3), low=-1, high=42)