remus: add wikipage link to remus README

http://nss.cs.ubc.ca/remus/ does not exists, replace it
with Remus wikipage.

Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Shriram Rajagopalan <rshriram@cs.ubc.ca>

docs/README.remus

@@ -1,4 +1,4 @@
 Remus provides fault tolerance for virtual machines by sending continuous
 checkpoints to a backup, which will activate if the target VM fails.
 
-See the website at http://nss.cs.ubc.ca/remus/ for details.
+See the website at http://wiki.xen.org/wiki/Remus for details.