DOC: Fix license link

Author: zbrookle

README.md

@@ -2,7 +2,7 @@
 
 ![CI](https://github.com/zbrookle/dataframe_sql/workflows/CI/badge.svg)
 [![Downloads](https://pepy.tech/badge/dataframe-sql)](https://pepy.tech/project/dataframe-sql)
-[![PyPI license](https://img.shields.io/pypi/l/dataframe_sql.svg)](https://pypi.python.org/pypi/dataframe_sql/)
+[![PyPI license](https://img.shields.io/pypi/l/dataframe_sql.svg)](https://github.com/zbrookle/dataframe_sql/blob/master/LICENSE.txt)
 [![PyPI status](https://img.shields.io/pypi/status/dataframe_sql.svg)](https://pypi.python.org/pypi/dataframe_sql/)
 [![PyPI version shields.io](https://img.shields.io/pypi/v/dataframe_sql.svg)](https://pypi.python.org/pypi/dataframe_sql/)