update the micro SD card's README (issues #79 and #83)

uSDCard/README.md

@@ -2,6 +2,13 @@ _mpmd_marlin_1.1.x_
 
 ## MPMD_MARLIN_1.1.X
 
+> ###### IMPORTANT CAVEAT! The `mpmd_marlin_1.1.x` firmware is __NOT__
+> ###### designed for the __V2__ model of the Monoprice Mini Delta
+> ###### 3D printer. Monoprice recently began selling a __V2__ model of
+> ###### the printer, and I doubt that this firmware is compatible.
+> ###### ___Please, do NOT try to install this firmware on the Monoprice
+> ###### Mini Delta V2 printer.___
+
 __an open-source upgrade for the Monoprice MP Mini Delta 3d printer__
 
 The [mpmd_marlin_1.1.x](https:/github.com/aegean-odyssey/mpmd_marlin_1.1.x)
@@ -11,6 +18,12 @@ zip archive to enhance your Monoprice MP Mini Delta 3d printer.
 
 ## GETTING STARTED
 
+Note: you'll need a micro SD card to install the firmware. The printer can
+be finicky about the card (more about this at the project's wiki), but the
+micro SD card that Monoprice supplies with the printer usually works. _It's
+a good idea to hang on to this card the comes with the printer, if only to
+be able to update the firmware if necessary._
+
 Copy the contents of this folder to the ROOT directory of the micro SD card,
 i.e. this README.md file should be in the card's ROOT directory. With the
 micro SD card, you can install the firmware, perform an initial printer