Fixed various typos/cutpasta
Merge pull request #89 from squaremo/proofread-readme

Fixed various typos/cutpasta
perform a 'refresh' on cm.status
so that we don't end up reporting targets under 'reconnects' that we
are already connected to.
Restructure attach and detach

To make the control flow more obvious.
Route multicast packets across the weave network

Add a route to send multicast packets to ethwe and so across the weave
network.

Without that, multicast packets get sent to the default route, i.e.
to docker's eth0 interface, rather than across the weave network.
So IP multicast doesn't work between containers on different hosts,
even though weaver supports it.