discretemod predict typo

[joep]

in a branch not exercised there is a typo .results instead of _results

>>> logit_mod.predict(linear=True)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "c:\josef\eclipsegworkspace\statsmodels-josef-experimental-gsoc\scikits\statsmodels\discretemod.py", line 162, in predict
    return np.dot(exog, self.results.params)
AttributeError: 'Logit' object has no attribute 'results'
>>>

[joep (josef-pktd)]

fixed in my branch and will push to devel