Can't use index as a function
Merge pull request #34 from Metaswitch/better-clustering-order

[No review needed] Can't use index as a function
Use split-horizon DNS to resolve Sprout addresses for memcached cluster
Merge pull request #35 from Metaswitch/memcached_public_hostname

{Reviewer: Andy} Use split-horizon DNS to resolve Sprout addresses for memcached cluster
Merge remote-tracking branch 'origin/master' into aio_node_ami
Code review markups