Updating to the current HEAD of the Tensorflow-Haskell bindings allows
us to also update the dependencies, specifically proto-lens, and avoid
having to retain their outdated versions.
The configuration-tensorflow.nix file specified several overrides for version
0.2.x packages, but those packages are no longer included in our package set
because they are so old. (Current versions seem to be in the range of 0.6.x.)
I fixed the evalution errors, but I did not verify whether these packages
actually build with the newer versions.
