webhook_inspector.py not py3 

https://github.com/Asana/devrel-examples/blob/master/python/webhooks/webhook_inspector.py is not python3 compatible. For example:

```
project = None
if 'ASANA_PROJECT' in os.environ:
    project = os.environ['ASANA_PROJECT'] 
else:
    print "No value for ASANA_PROJECT in env" 
    quit()
```