Update README to use new single weave launch command

[awh]

Defer merge until #962 is released.

[rade]

I'd like to go a bit further here, if possible, and excise any mention of weaveDNS or the proxy from the README. On that note, I have been wondering whether we should rename weave proxy-[env|config] to just weave env|config (new issue, obviously).

[rade]

This PR can become an accumulator for all the README changes that need to be merged at release time. I suggest we put the branch into the main repo, so its easier for everybody to work on it.

[awh]

excise any mention of weaveDNS or the proxy

I'll give it a go.

On that note, I have been wondering whether we should rename weave proxy-[env|config]

Seems reasonable.

I suggest we put the branch into the main repo, so its easier for everybody to work on it.

Good idea. I'll have to close this PR and make a new one.

[rade]

I have raised #1014 for weave env|config.