support v1 auth

This should do the trick. 

Verified `st_auth` values:
* https://zebra.zerovm.org/auth/v1.0
* https://identity.api.rackspacecloud.com/v1.0

This shouldn't interfere with any existing v2 auth support.

- [x] Still needs CLI work, probably in `arguments/__init__.py`


##### Added command line args:
* `--st-auth` ( defaults to `$ST_AUTH` )
  * mutually exclusive w/ `--os-auth-url`
* `--st-user` ( defaults to `$ST_USER` )
  * mutually exclusive w/ `--os-user`
*  `--st-key` ( defaults to `$ST_KEY` )
  * mutually exclusive w/ `--os-apikey` & `--os-password`