add python-webob as dependency

[Patrick Hetu]

With the lastest version: 0.1+bzr58-1.1

<pre>
flocon:/tmp/testwiki$ wikkid-serve .
Traceback (most recent call last):
  File "/usr/bin/wikkid-serve", line 24, in <module>
    from wikkid.app import WikkidApp
  File "/usr/lib/python2.7/dist-packages/wikkid/app.py", line 16, in <module>
    from webob import Request, Response
ImportError: No module named webob
</pre>

[Tim Penhey (thumper)]

Done at the sprint too.