Adds continuation param to get() and post().

[halfak]

Implements automatic continuation of result JSON docs if the continuation param is True.

[halfak]

Note that I chose to implement continuation on top of get() and post() methods. This means that the return value of these function is different depending on the value of a parameter. This may be undesirable, so consider it in your review.

FWIW, it seems like this is the best option to me. It seems that the two return types (either a JSON dict or a generator of JSON dicts) is intuitive.