Use a regular expression to parse GCodes

This should parse parentheses correctly and handle (valid) gcodes such as
G1X2Y3, while before we were assuming spaces between tokens (which is wrong as
per the G-Code spec). This should fix req #333 in a clean and systematic way.
This is also a component for #343 (Marlin M114 response is in the form ok C:
X11Y22Z33E44, which we can parse with the same expression).

printrun/gcoder.py

@@ -20,6 +20,7 @@ import math
 import datetime
 
 gcode_parsed_args = ["x", "y", "e", "f", "z", "p", "i", "j"]
+gcode_exp = re.compile("\([^\(\)]*\)|[/\*].*\n|\n|[a-z][-+]?[0-9]*\.?[0-9]*") 
 
 class Line(object):
 
@@ -46,7 +47,7 @@ class Line(object):
         self.raw = l.lower()
         if ";" in self.raw:
             self.raw = self.raw.split(";")[0].rstrip()
-        self.split_raw = self.raw.split(" ")
+        self.split_raw = gcode_exp.findall(self.raw)
         self.command = self.split_raw[0].upper() if not self.split_raw[0].startswith("n") else self.split_raw[1]
         self.is_move = self.command in ["G0", "G1"]