make the consumer python2 for now. *cries*
    
    per threebean, fedmsg signature validation does not work in
    Python 3 ATM, for...reasons. It's not a good idea to deploy a
    production listener which doesn't validate message signatures,
    so let's make the consumer py2 for now.
    
    Add a convenience wrapper for the consumer, like the one for
    the CLI.
    
    Note that whether you get py2 or py3 binaries from 'setup.py
    install' still depends on whether you run it with py2 or py3,
    whatever the hashbang in these files says. In the RPM package
    I'll just mung the appropriate hashbangs.