Doc improvements for deploy-sourcegraph-dot-com

Created by: nicksnyder

I don't understand the semantic difference between https://github.com/sourcegraph/deploy-sourcegraph-dot-com/blob/release/README.info.md https://github.com/sourcegraph/deploy-sourcegraph-dot-com/blob/release/README.dev.md

It also seems like a waste that the root README.md is basically empty.

Can you consolidate all the relevant information into https://github.com/sourcegraph/deploy-sourcegraph-dot-com/blob/release/README.md?