Add G02/03 arc conversion/pre-processor script and example streaming script

Beta pre-processor script used to clean and streamline g-code for
streaming and converts G02/03 arcs into linear segments. Allows for full
acceleration support if the pre-processed g-code is then streamed to
grill, sans G02/03 arcs. Added a simple example streaming script for
Python users.

script/simple_stream.py

@@ -0,0 +1,33 @@
+#!/usr/bin/env python
+"""\
+Simple g-code streaming script for grbl
+"""
+
+import serial
+import time
+
+# Open grbl serial port
+s = serial.Serial('/dev/tty.usbmodem1811',9600)
+
+# Open g-code file
+f = open('grbl.gcode','r');
+
+# Wake up grbl
+s.write("\r\n\r\n")
+time.sleep(2)   # Wait for grbl to initialize 
+s.flushInput()  # Flush startup text in serial input
+
+# Stream g-code to grbl
+for line in f:
+    l = line.strip() # Strip all EOL characters for consistency
+    print 'Sending: ' + l,
+    s.write(l + '\n') # Send g-code block to grbl
+    grbl_out = s.readline() # Wait for grbl response with carriage return
+    print ' : ' + grbl_out.strip()
+
+# Wait here until grbl is finished to close serial port and file.
+raw_input("  Press <Enter> to exit and disable grbl.") 
+
+# Close file and serial port
+f.close()
+s.close()