Documentation updates
Eliminate the RAX_REGION environment variable; iterate through all regions available to an account and present servers in region groups; default to using server name to identify servers in groups; set ansible_ssh_host key for each server; utilize the _meta key to provide all the hostvars for each server; all grouping by web, db, sql, lb, app based on server name; pretty print JSON output for some human-readable inventory action

Add set_setting to alleviate requirement that ~/.pyrax.cfg exists

Add regions as a optional env var to narrow our inventory scope

Clean up
Documentation updates for region env var
Accept a comma-separated list of regions
Remove grouping of hosts by trying to discern subdom in server name
Make creds file env var optional; look for ~/.rackspace_cloud_credentials if not supplied
Implement @cchurch suggestions
Move regions until after authentication; otherwise pyrax.regions is an empty tuple and no inventory is returned.
Merge pull request #4326 from angstwad/devel

Revamp of the rax.py inventory plugin