Revert "[KNIFE-437] remove default region and make region required"

This reverts commit 5d9b96449bcf0e279174b86eddaa9932629bc1bd.
removing default_region
Merge branch 'master' of https://github.com/opscode/knife-rackspace
increasing fog dependency to ~> 1.16
Merge pull request #74 from rackspace/fog_116

increased fog version to fog ~> 1.16