Added urllib2.HTTPError to except clause in binary method

This Pull Request addresses issue #58 :

I have added urllib2.HTTPError to the try/except block in the method binary on line 117 and made sure the NotFoundException gets called in all instances in case the retry limit is exceeded.

@whimboo This fixes the issue that you have seen, but if you feel this is insufficient, then just as usual drop a line and give suggestions.

Thanks