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)
> Not only your users will, but helps us with hosting

Not only will your users, but it helps us with hosting and promoting good practices (something along these lines - link to a blurb about minified file benefits).