Change default value of parametr of GenerateSubdivisions()

Change default value of parallel from 1 to 0, so we can
use parmap with parallel = 1 to measure slowdown caused
by interprocess communication.

groupConnectivity.pyx

@@ -91,12 +91,12 @@ def subdivisionIterator(G, edges = None):
 
 def generateSubdivisions(file, G, edges = None,
                          function = lambda H: H.graph6_string(),
-                         parallel = 1):
+                         parallel = 0):
   f = open(file, 'w+')
   f.write("# Subdivisions of edges '%s' of graph '%s' (%s)\n" %
           (edges, G.graph6_string(), G))
 
-  if parallel == 1:
+  if parallel == 0:
     iterator = map(function, subdivisionIterator(G, edges))
   else:
     iterator = parmap(function, subdivisionIterator(G, edges), parallel)