Provide API for building AuthOptions from env vars.
Recognize OS_REGION_NAME if env var is set.

Also, provide an out in case you really, really want to ignore this
environment variable.
Forgot to include osutil sub-package.
Merge pull request #115 from rackspace/gh-112-openstack-env-vars

Provide API for building AuthOptions from env vars.
Add support for floating IPs using nova API.

When using vanilla OpenStack with neutron, instances are commonly
accessible from the outside world only by using floating IPs.

This patch adds support for:
  - listing floating IPs
  - allocating a floating IP from a given pool
  - attaching a floating IP to an instance
  - de-allocating an IP and returning it to its pool.
Merge pull request #121 from echohead/floating-ips-rax

Add support for floating IPs using nova API.
Added security group field to NewServer struct in servers.go