Update README.md

Updated link to usage.md

Author: jimlehner

README.md

@@ -158,7 +158,7 @@ The `xmr_comparison` function generates a grid of XmR charts that contain proces
 
 ## Configuration and Usage
 
-Configuration and usage details for each function can be found in [USAGE.md](docs/USAGE.md)
+Configuration and usage details for each function can be found in [USAGE.md](USAGE.md)
 
 ## Project Structure