BLD: pymysql 0.6.6
looks like `pymsyql` just got updated from 0.6.3 to 0.6.6, see here: https://travis-ci.org/pydata/pandas/jobs/53409636

[changelog](https://github.com/PyMySQL/PyMySQL/blob/master/CHANGELOG)

and started breaking our builds (only 3.4 oddly)
