v0.2

Update for Tensorflow 2.0.

Improvements

• Added VectorSpace class to store vector information, and to avoid having to recalculate the pd_graph repeatedly.
• Added Minimizer class to facilitate easy use of the optimization functions.
• Tested a number of different
• Generalized vectors.py to_ratio and closest_from_log methods to work with any number of elements (but generally with a 3-dimensional Tensor).