xlrd is required for handle excel in pandas but it is EOL and yield warnings on py37
Hello,

To use `pandas.read_excel` and `pandas.DataFrame.to_excel` we need xlrd.

xlrd is EOL, and can be replaced with OpenPyXL Do you plan this migration ?

Moreover, now xlrd yield warnings with python 3.7

```
xlrd/xlsx.py:266: PendingDeprecationWarning: This method will be removed in future versions.  Use 'tree.iter()' or 'list(tree.iter())' instead.
    for elem in self.tree.iter() if Element_has_iter else self.tree.getiterator():

```

```
xlrd/xlsx.py:312: PendingDeprecationWarning: This method will be removed in future versions.  Use 'tree.iter()' or 'list(tree.iter())' instead.
    for elem in self.tree.iter() if Element_has_iter else self.tree.getiterator()
```


