added infos for this fork

README.md

+SCUBA82's fork:
+-----------------
+
+The main goal of my fork is porting the brilliant Marlin firmware to GEN7 Boards.
+I'm working on a 16MHz GEN7 board and have only tested with this configuration.
+But there were reports about successfully running it at 20 MHz. Expect 25% faster moves and maybe some other issues.
+
+Using lcd and sdcard support on an ATMega644(P) is not possible cause the sketch is way too big for its memory.
+I switched to an ATMega1284P which has double size program memory. Unfortunately it's not supported in Arduino IDE out of the box but expect a tutorial on how to compile for it soon. 
+For the necessary pin breakouts I used Alfons3 design of GEN7 (https://github.com/Alfons3/Generation_7_Electronics) with an additional breakout for pin A0/D31. 
+I'll publish my desing as soon as possible.
+
+Expect this fork to be highly experimental. 
+
 WARNING: 
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 THIS IS RELEASE CANDIDATE 1 FOR MARLIN 1.0.0