Version prefix

In case the REST URL is prefixed by variables, I've add a reduce_path function in SETTINGS to remove them from diaplaying urls.

For example, if URL begins with (?P<version>[\w.]+)/(?P<partner>[\w-]+)/myurls, then SETTINGS = {
....
        'api_path': '/0.1/partner/',
        'reduce_path': lambda x: x[x.rfind('}')+1:]
....

The lambda function for reduction should be defined accordingly to prefix to be removed