Storage swift alt

@ustudio/dev for your consideration...

add swift storage alternatives for storage library
- add support for OpenStack Swift based storage (non-rackspace)
- add `register_swift_protocol` decorator to facilitate adding Swift endpoints.
  - requires a `scheme` (e.g. "hpcloud") and `auth_endpoint` when wrapping
    a `CloudFilesStorage` subclass.
  - exports decorator at toplevel along with `get_storage()`
- add HPCloudStorage endpoint to support HP Helion cloud storage
  - storage uri's have the format:
      `hpcloud://user:pass@container/obj?region=REGION&tenant_id=ID`
- includes unit tests for changes
- updated docs to include info on `swift` and `hpcloud` schemes.
at the moment, no.  in fact, because of the defensive programming you made a comment on below, not specifying a `region` would actually raise an exception.  

i could modify the decorator to include not only the `auth_endpoint` but the `region` as well?  But then the `hpcloud` scheme would be tied down to a specific region instead of generalized for all HP Helion object stores.  (this assumes that the specified `auth_endpoint` actually works across regions of course and isn't tied to a specific region itself.)