title: How can I get columns from Multi-Index?
body: <p>I have a dataframe called "keytable" which features a Multi-Index composed of 'Month', 'Day' and 'Hour'. I want to keep that multi-index while creating 3 new columns with the values of 'Month', 'Day' and 'Hour'. How can I do it?
  Here's the dataframe:</p>
  
  <pre><code>keytable.head()
  Out[59]: 
                   pp    pres  rad    rh  ...   ws  WeekDay   Power_kW  Power_kW18
  Month Day Hour                          ...                                     
  1     3   0     0.0  1027.6  4.1  78.9  ...  0.0        3  77.303046  117.774419
            1     0.0  1027.0  3.3  79.7  ...  0.0        3  72.319602  110.710928
            2     0.0  1027.0  3.3  81.8  ...  0.0        3  71.831852  106.067667
            3     0.0  1027.0  1.9  86.6  ...  0.0        3  69.555751  106.325955
            4     0.0  1027.0  3.8  92.2  ...  0.0        3  69.525780  102.855393
  
  [5 rows x 11 columns]
  </code></pre>