fix issues 5 and 6

The mobile-frontend server crashes currently with this error:

```
Traceback (most recent call last):
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/runtime/wsgi.py", line 267, in Handle
    result = handler(dict(self._environ), self._StartResponse)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.3/webapp2.py", line 1519, in __call__
    response = self._internal_error(e)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.3/webapp2.py", line 1511, in __call__
    rv = self.handle_exception(request, response, e)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.3/webapp2.py", line 1505, in __call__
    rv = self.router.dispatch(request, response)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.3/webapp2.py", line 1253, in default_dispatcher
    return route.handler_adapter(request, response)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.3/webapp2.py", line 1077, in __call__
    return handler.dispatch()
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.3/webapp2.py", line 547, in dispatch
    return self.handle_exception(e, self.app.debug)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.3/webapp2.py", line 545, in dispatch
    return method(*args, **kwargs)
  File "/Users/peterliu/Development/appengine-modules-helloworld-python/printenv.py", line 107, in get
    html_for_modules_method('get_num_instances'),
  File "/Users/peterliu/Development/appengine-modules-helloworld-python/printenv.py", line 73, in html_for_modules_method
    value = method(*args, **kwargs)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/api/modules/modules.py", line 271, in get_num_instances
    _ResultHook).get_result()
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/api/apiproxy_stub_map.py", line 613, in get_result
    return self.__get_result_hook(self)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/api/modules/modules.py", line 259, in _ResultHook
    _CheckAsyncResult(rpc, mapped_errors, {})
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/api/modules/modules.py", line 146, in _CheckAsyncResult
    raise mapped_error()
InvalidVersionError
```

The culprit is the call to ```html_for_modules_method('get_num_instances')``` which seems to work if you change automatic scaling to manual scaling.