mention configargparse in readme

pseewald · pseewald · commit 2c68f2a64aa4 · 2019-05-23T17:36:16.000+02:00
diff --git a/README.md b/README.md
@@ -24,7 +24,8 @@ fprettify is an auto-formatter for modern Fortran code that imposes strict white
 
 ## Requirements
 
-Python 2.7 or Python 3.x
+* Python 2.7 or Python 3.x
+* [ConfigArgParse](https://pypi.org/project/ConfigArgParse): optional, enables use of config file
 
 
 ## Examples
