Add note to readme

README.md

@@ -54,3 +54,12 @@ one of {LR,RL,DU,UD,DLUR,URDL,ULDR,DLUR}, edge is one of * (any), N (none), L (l
   - Example: `lisgd -t 400`
 - **-v**: Verbose mode, useful for debugging
   - Example: `lisgd -v`
+
+---
+
+All changes below this line have come from Jonathan
+
+## Usage
+
+I spent an embarrassingly long amount of time trying to work out why this wasn't
+working. Be sure that your user is in the `input` group before running it.