Document the deployment procedure

[goerz]

This should clarify some of the details mentioned in the doctr deploy documentation, specifically what "synchronization" is (--no-sync flag), and how --command fits in.

[goerz]

Hopefully, I got the procedure right, based on looking over the source code. Let me know if I misunderstood anything.

One question: What is the purpose of the --no-temp-dir flag? It skips the first step, copying the BUILT_DOCS directory, but I can't think of any situation where this would be useful. I think it would cause a crash unless combined with --no-sync. I suppose with --no-temp-dir and --no-sync, a custom --command could take over the entire deployment, but it wouldn't have access to the built documentation (which was stashed away).

[asmeurer]

I don't remember why I added it (see #215). It might have been for the reason you noted so that you can control the deployment yourself if you want. But the stash thing was added later, so it might be broken. It looks like the flag isn't tested, so I'm not surprised if it doesn't work.