Add readme.md

README.md

+## installation:
+
+Just download the file and/or clone this git repository and give execution permissions to the grl2gcode.py python script.
+There are no external dependencies except for python itself.
+
+The script should be able to run on almost any system providing python is installed, it should work with both python 2.x and 3.x
+and with any standard excellion drill file 
+
+Tested on Devuan GNU/Linux only and with kicad.
+
+## Usage:
+
+Using kicad generate an excellion drill file using metric measurements and
+auxiliary axis as drill origin after pointing grid origin on the bottom left
+of your PCB design.
+
+Then, launch ./grl2gcode.py passing as the only argument the file name of the 
+generated .drl excellion file.
+
+
+Editing grl2gcode.py you will find some variables you can tweak:
+
+ * SPINDLE_SPEED = 32000
+ * XY_MOVE_SPEED = 3000
+ * Z_MOVE_SPEED = 300
+ * DRILL_MOVE_SPEED = 100
+ * DRILL_DEPT = 2
+ * SAFE_HEIGHT = 25
+ * RUNNING_HEIGHT = 10
+ * TOOL_HEIGHT = 40
+ 
+