update README

Made 3 distinct steps, clarified packaging, moved running bot at end (not needed by most people), ensured correct capitations.

Diff is confusing; easier just to [read directly](https://github.com/tomByrer/libgrabber/blob/master/README.md)
"that we host" in that case is a ["restrictive relative clause"](http://en.wikipedia.org/wiki/That).  It further defines 'projects'.