Added Travis-CI configuration file

Based on Tox, same as the iPOPO Travis configuration file.
Added __call__ and __close methods to ServerProxy

- Allows to use the 'client("close")()' method to close the
  transport layer of a ServerProxy, even on Python 2.6
  => Fixes #2
- Updated tests to _really_ close the transport layer
  (and not just to retrieve the closing method)
XMLTransport.close() was also added in Python 2.7

Finally fixes #2
Version increment, related to issue #2

Also added supported Python versions to setup.py
initial WSGI support that works on 2.7
WSGI should decode incoming JSON

Note that it seems that people don't declare the encoding in
Content-Type so I'll just assume people want to use the encoding that
the server uses internally :)