CI/DOC: doc build is failing

[jreback]

This is the latest: https://travis-ci.org/pandas-dev/pandas/jobs/472753353

though seems to have been failing since dec 15th, the last updates: http://pandas-docs.github.io/pandas-docs-travis/

[jreback]

cc @datapythonista @TomAugspurger

[datapythonista]

seems like a problem with the git commands, I'll take a look in a minute