CLN/API: wide_to_long or lreshape
xref https://github.com/pandas-dev/pandas/issues/2567

```
In [27]: data = pd.DataFrame({'hr1': [514, 573], 'hr2': [545, 526],
    ...:                       'team': ['Red Sox', 'Yankees'],
    ...:                       'year1': [2007, 2008], 'year2': [2008, 2008]})
    ...: 

In [28]: data
Out[28]: 
   hr1  hr2     team  year1  year2
0  514  545  Red Sox   2007   2008
1  573  526  Yankees   2008   2008

In [29]: pd.lreshape(data, {'year': ['year1', 'year2'], 'hr': ['hr1', 'hr2']})
Out[29]: 
      team  year   hr
0  Red Sox  2007  514
1  Yankees  2008  573
2  Red Sox  2008  545
3  Yankees  2008  526

In [30]: pd.wide_to_long(data, ['hr', 'year'], 'team', 'index')
Out[30]: 
                hr  year
team    index           
Red Sox 1      514  2007
Yankees 1      573  2008
Red Sox 2      545  2008
Yankees 2      526  2008
```

So we should drop one of these.