COMPAT: openpyxl
Just noticed in one of the test suites:

```
home/travis/miniconda/envs/pandas/lib/python3.4/site-packages/openpyxl/worksheet/worksheet.py:300: UserWarning: Using a coordinate with ws.cell is deprecated. Use ws[coordinate] instead

  warn("Using a coordinate with ws.cell is deprecated. Use ws[coordinate] instead")
```
