Documentation issue

[ironmanaudi]

I notice that there is no materials about variational quantum eigensolvers (VQE) in the documentation of OpenFermion. I suppose the algorithm is a hot spot for the lastest researches of quantum computing. Also, without official document, it is hard to find a up-to-date demo code for researcheres to carry out VQE experiments, which could cause some trouble. It would be lovely to add some demo code to the official documentation, like, using UCCSD ansatz to get the ground state energies for LiH.