title: What are the new statsmodels dependencies, specifically regarding pandas.WidePanel?
body: <p>I'm trying to run an ARMA model using statsmodels.tsa.ARIMA.ARMA, but I get AttributeError: module 'pandas' has no attribute 'WidePanel'. Are there some weird dependencies I should be worried about? Why can't I run this ARMA?</p>
  
  <p>I'm using statsmodels==0.9.0 and pandas==0.23.0 (I had to downgrade my pandas version because the deprecation of pandas.core.datetools disallowed me from calling statsmodels.tsa.statstools.acf). </p>
  
  <pre><code>ma = ARMA(endog = amy_dict['DBM']['tot_conv'],
            order = (1,0))
  </code></pre>