Make Node a subclass of Tensor?

[repst]

Having not followed the recent PRs, our group became aware of the new Tensor class with the release of 0.4.2. We found that tensornetwork.ncon, tensornetwork.conj and tensornetwork.node now take Tensor objects and throw errors when passed Node objects. If Node inherited from Tensor they could share such functionality. I think of a node as a tensor with extra ability to connect to other nodes.

What do you think of this solution rather than wrapping Node around Tensor as discussed in #848?