Whitespace.
Making `Client(api_key_file)` a valid auth identifier.

Previously it was called `Client(api_key_file_location)` -- this makes things
match our naming conventions with the other SDKs.

For backwards compatibility, api_key_file_location is still respected.
Updating mock tests for `Client(api_key_file)`.
Making `Client(api_key_id, api_key_secret)` valid.

This is in favor of `Client(id, secret)` -- and normalizes our naming
conventions.
Making our client load from environment variables automatically.
Updating changes.
Adding tests for environmental auth.
Whitespace.
Fixing bad import.
Updating the README to reflect the new configuration stuff.
Making the Client auto-detect ~/.stormpath/apiKey.properties.
Adding changelog info.
Version bump.