Fix some `print` and `except` statements for 3.x.

- With these changes, and MichalMazurek's `gevent` fork
  (from [#38](https://github.com/surfly/gevent/issues/38)),
  I'm able to build `zerorpc` for Python 3.4.

- No promises on whether it actually starts up, much less works properly. I was just looking to see how far this library was from 3.x compatibility, and this was all it took to get `pip3 install .` to work.