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.
Ok.  I'll switch it around.  

I went with this since it was a bit of a time-saver (not having to migrate all the `CloudFilesStorage` methods to the `SwiftStorage` class and of course migrate all the existing unit tests to test those methods against `SwiftStorage` instead of `CloudFilesStorage`)  but you are right.  `SwiftStorage` really should be the super class.