fix all tests under Python 3

Author: psviderski

chem/miller.py

@@ -1,4 +1,5 @@
 """ Calculation of Miller indices """
+from functools import reduce
 
 import numpy as np
 import math

chem/tests.py

@@ -9,14 +9,14 @@
     chemical_equations_equal,
 )
 
-import miller
+from . import miller
 
 local_debug = None
 
 
 def log(s, output_type=None):
     if local_debug:
-        print s
+        print(s)
         if output_type == 'html':
             f.write(s + '\n<br>\n')