Add Mega-S extruder settings to readme

Close #33

README.md

@@ -70,9 +70,11 @@ I provided three different precompiled hex files: One for no modifications on th
 - `M502` - load hard coded default values
 - `M500` - save them to EEPROM
 
-**If you are using this on a Mega-S, those two additional commands are necessary:**
+**If you are using this on a Mega-S, those four additional commands are necessary:**
 - `M92 E384` - set correct steps for the new extruder
-- `M500` - save them
+- `M203 E30` - limit extruder feedrate
+- `M204 R1500.00` - lower retract acceleration
+- `M500` - save the values
 - I highly recommend calibrating the extruder.
 
 #### Calibration and other instructions have been moved to the [Wiki](https://github.com/davidramiro/Marlin-AI3M/wiki/Calibration).