Versioneer reported version of dev build is incorrect
Sometimes it's nice to install projects from master to get recent fixes (e.g. `pip install git+https://github.com/pandas-dev/pandas.git`). However, since pandas switched to using dev branches for `0.19.1+`, versioneer incorrectly reports the version of the dev build as `0.19.0`. This breaks checks for version, e.g. the following would report false for a build off master, when semantically master is after the 0.19.2 release:

```python
from distutils.version import LooseVersion
import pandas as pd

LooseVersion(pd.__version__) > '0.19.2'
```

I'm not sure if there is an easy/good fix for this, just opening this to discuss.