Add the turtle commands tot he help

SimpleTurtle/Help.txt

@@ -16,6 +16,13 @@ Input File Format:
     Subsequent lines beginning with a # (hash sign) are ignored.
     Rules are declared with an equals sign - i.e. f=f-f+, or fb=fbfafcfafb.
     Lines starting with an exclamation mark specify directives that should be passed to the turtle - i.e. !angle=1.0472
+    The L-System is rendered at each generation. Any character the turtle doesn't understand is ingored.
+
+    Turtle Characters:
+        f   Move forwards
+        h   Also move forwards
+        +   Turn clockwise
+        -   Turn anti-clockwise
 
     Turtle Directives:
         angle    Sets the angle by which the turtle should turn. Note that this is specified in radians.