Fix version detection for all Python versions

Inspecting sys.version_info using named component attributes was added in
the patch "Some fixes to start support for python3."

Named component attributes were only added to sys.version_info in Python
2.7 so their use breaks Cura for Python 2.6.

As Cura otherwise works in the still widely used Python 2.6 it seems best
to maintain this compatibility.

Cura/cura_sf/fabmetheus_utilities/euclidean.py

@@ -37,7 +37,7 @@ import sys
 import math
 import random
 
-if sys.version_info.major < 3:
+if sys.version_info[0] < 3:
 	import cStringIO
 else:
 	import io as cStringIO

Cura/cura_sf/fabmetheus_utilities/gcodec.py

@@ -29,7 +29,7 @@ import os
 import sys
 import traceback
 
-if sys.version_info.major < 3:
+if sys.version_info[0] < 3:
 	import cStringIO
 else:
 	import io as cStringIO

Cura/cura_sf/fabmetheus_utilities/xml_simple_writer.py

@@ -10,7 +10,7 @@ import __init__
 
 import sys
 
-if sys.version_info.major < 3:
+if sys.version_info[0] < 3:
 	import cStringIO
 else:
 	import io as cStringIO

Cura/util/profile.py

@@ -4,7 +4,7 @@ from __future__ import division
 import __init__
 
 import os, traceback, math, re, zlib, base64, time, sys
-if sys.version_info.major < 3:
+if sys.version_info[0] < 3:
 	import ConfigParser
 else:
 	import configparser as ConfigParser