Python 3 support

If we do not coerce non-binary types to UTF-8, then in Python 3, every ```body``` would have to be encoded with UTF-8 prior to passing to ```send()```, including all the functions in nsq that pass in a ```str```.  We would have to encode all strings in any case. In Python 2, this is less of an issue because ```str``` is treated as a binary type.  Are you sure you want this?