Fix for unexpected decoding errors. 

Now pythonwhois no longer raises a `UnicodeDecodeError` whenever a response uses a non-UTF-8 encoding. It instead goes through UTF-8 and ISO-8859-1, and is easily extensible to other encodings Python supports. If it goes through the entire list of encodings without managing to decode the page, it raises a `ValueError` with the server in it for easy error spotting.

This should fix issue #57, but I'll leave that determination to someone else. As noted in that issue's comments, there could be other ways to do this.