Linking to OpenFermion

[babbush]

@dabacon @Strilanc

On OpenFermion-Cirq we prominently link to Cirq towards the top of the readme and we will do the same on OpenFermion once Cirq and OpenFermion-Cirq are live. Would it make sense to have something somewhere in the readme of Cirq that says something like "For those interested in quantum simulation, checkout OpenFermion-Cirq(link) which uses OpenFermion(link) for compiling algorithms to simulate chemistry and materials using Cirq." I could take a stab at this if you were amenable to something like that.

[Strilanc]

I think that's reasonable. Some sort of "see also" section.

[babbush]

yeah