[rackspace|compute_v2] added specific exception for invalid states in order to make it easier to rescue.
Merge branch 'master' of github.com:fog/fog into ready_exception
merging in latest master
Merge branch 'master' of github.com:fog/fog into ready_exception
[rackspace] adding note about credentials in the getting started document
Revert "[rackspace] adding note about credentials in the getting started document"

This reverts commit c5637517bee1a571bb1358cd70d8318fabf411fe.
Merge pull request #1697 from rackspace/ready_exception

[rackspace|compute_v2] Ready Exception