Added support for the `log_file` attribute when creating the server.  Allows
you to redirect the access log to a file (or /dev/null) instead of `stderr`
as pywsgi does it by default.

This also works in the .ini through the "paster" integration thing.
On the __init__.py the socketio_manage() uses the environ 'socketio' but here it was using 'socket.io', this was causing a KeyError when using gunicorn.
Fixing tests.
Fixing decimal conversion string for Python 2.6.