Add link to matminer in readme

Author: ardunn

README.md

@@ -7,7 +7,7 @@ automatminer is an automatic prediction engine for materials properties.
 [![Codacy Badge](https://img.shields.io/codacy/coverage/aa63dd7aa85e480bbe0e924a02ad1540.svg?colorB=brightgreen)](https://www.codacy.com/app/ardunn/automatminer)
 [![PyPI version](https://img.shields.io/pypi/v/automatminer.svg?colorB=blue)](https://pypi.org/project/automatminer/)
 
-Note: As of this writing, automatminer requires the newest version of matminer (from GitHub) to work properly. 
+Note: As of this writing, automatminer requires the newest version of [matminer (from GitHub)](https://github.com/hackingmaterials/matminer) to work properly. 
 
 - **Website (including documentation):** <https://hackingmaterials.github.io/automatminer>
 - **Help/Support:** <https://groups.google.com/forum/#!forum/matminer>