Added ability to upload data received from stdin.
Added `secure` parameter to `get_item_metadata()` (HTTP/HTTPS) -- Use HTTP by defualt. Added ConnectionError exception to `get_item_metadata()` if Metadata API does not return a 200 status code.
Updated doc strings. Use `secure=False` as defualt. Do not fail if unable to get sizehint for file-like object, simply do not include a sizehint.