Request to define a ``newbytes3`` type for Py3.3 and Py3.4 only with % formatting (backport of PEP 461 from Py3.5)

[edschofield]

This request is for a subclass of bytes on Py3.3 and Py3.4 that backports % formatting from Py3.5 (PEP 461).

See also issue #54.

See http://bugs.python.org/issue20284 for sample implementations in C :-/

[jmadler]

I believe this is addressed by #359
Please reopen if I may be mistaken :)