Corrected reference to arg array when it's easier to use the helper function

Author: moebrowne

README.md

@@ -101,8 +101,8 @@ The order the arguments are passed on the command line makes a difference
 
 ### Examples
 
-* Calling `my-script.sh -f first -f last` will cause `${args["f"]}` to have the value `last`
-* Calling `my-script.sh -g 345 -g` will mean cause `${args["g"]}` to be blank
+* Calling `my-script.sh -f first -f last` will cause `argValue "f"` to return the value `last`
+* Calling `my-script.sh -g 345 -g` will mean cause `argValue "g"` to return nothing
 
 ## Debug Mode