Decoding Error Exceptions

[jimcarreer]

We would like to throw exceptions in the event of a decoding error (Huffman or HPACK). This work some-what blocks Issue #2 since proper fuzz testing would only really be nice with some kind of error handling framework. I would like to include the byte position decoding began at as well as how far we read from the byte string before the error was encountered if possible. I think it might also be nice (but not necessary) to include the headers that were successfully decoded up to that point.

[MC874]

Yep, It still produce HPackDecodingError:

hpack.exceptions.HPACKDecodingError: Unable to decode HPACK integer representation from <memory at 0x7f8b75ee9d80>