Remove defunct Travis CI badge.

Author: matthewwardrop

README.md

@@ -20,7 +20,6 @@ building design matrices. Patsy brings the convenience of [R](http://www.r-proje
 ![PyPI - Python Version](https://img.shields.io/pypi/pyversions/patsy.svg)
 ![https://patsy.readthedocs.io/](https://img.shields.io/badge/docs-read%20now-blue.svg)
 ![PyPI - Status](https://img.shields.io/pypi/status/patsy.svg)
-![https://travis-ci.org/pydata/patsy](https://travis-ci.org/pydata/patsy.png?branch=master)
 ![https://coveralls.io/r/pydata/patsy?branch=master](https://coveralls.io/repos/pydata/patsy/badge.png?branch=master)
 ![https://doi.org/10.5281/zenodo.592075](https://zenodo.org/badge/DOI/10.5281/zenodo.592075.svg)