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.
It seems like there should be a generic way to register *any* protocol, and registering a swift-protocol sub-type should be built on top of that.