introduce app.intaddrs which are ec2 secondary IPs

requires introduction of app.azlimit which limits the availability zones
for an instance / autoscale group to a single AZ.  Subnets cannot span
AZs, so this is the only option.

ec2rotatehosts now detects the first secondary address and preserves it
GH #19 - external addresses fail with multiple

removes applied addresses from pool to avoid re-applying to another
instance in same iteration.
Merge pull request #18 from WrathOfChris/cm-ec2secondaryaddrs

introduce app.intaddrs which are ec2 secondary IPs
Merge pull request #20 from WrathOfChris/cm-19-multiple-addrs

GH #19 - external addresses fail with multiple