Merge pull request #693 from bboreham/677-document-rmpeer

Illustrate the usage of 'weave rmpeer'

Closes #677.

site/ipam.md

@@ -94,3 +94,24 @@ peer, and as such should be used with extreme caution - if the rm'd
 peer had transferred some range of IP addresses to another peer but
 this is not known to the whole network, or if it later rejoins
 the Weave network, the same IP address may be allocated twice.
+
+Assuming we had started the three peers in the example earlier, and
+host3 has caught fire, we can go to one of the other hosts and run:
+
+    host1$ weave rmpeer host3
+
+Weave will take all the IP address ranges owned by host3 and transfer
+them to be owned by host1. The name "host3" is resolved via the
+'nickname' feature of weave, which defaults to the local host
+name. You can see the full set of range assignments in the output from
+`weave status`, which will show the internal hex ID and nickname in
+brackets, like this:
+
+    Ring [10.2.1.1, 10.2.1.255)
+      10.2.1.1 -> 96:e9:e2:2e:2d:bc (host1) (version: 3, free: 126)
+      10.2.1.128 -> ea:84:25:9b:31:2e (host2) (version: 2, free: 64)
+      10.2.1.192 -> ea:6c:21:09:cf:f0 (host3) (version: 1, free: 62)
+
+So, in our example, we could equivalently do:
+
+    host1$ weave rmpeer ea:6c:21:09:cf:f0