Refactored class interfaces, bumped version to 0.0.6

1). renamed ``Client.request()``->``Client.__call__()``:
    request is an ambiguous term in the context of SnapSearch.
    It may refer to (a) the incoming HTTP request from the robot,
    or (b) the outgoing HTTPS request to SnapSearch backend.
2). renamed ``Detector.detect()``->``Detector.__call__()``:
    for a stateless ``Detector`` (introduced since 0.0.5 and
    reasoned in Development Memo III, Issue 11), ``detect()`` is
    the only functional method, it is more Pythonic to make the
    entire object callable through the ``__call__()`` method.
3). renamed ``Interceptor.intercept()``->``Interceptor.__call__()``:
    same reason as 2).