Move the code from appveyor config to a Python script

No more PowerShell rubbish, yay!

support/timer.py

@@ -0,0 +1,35 @@
+# A with statement based timer.
+
+from __future__ import print_function
+from contextlib import contextmanager
+import timeit
+
+class Timer:
+  """
+  A with statement based timer.
+  Usage:
+    t = Timer()
+    with t:
+      do_something()
+    time = t.time
+  """
+    
+  def __enter__(self):
+    self.start = timeit.default_timer()
+
+  def __exit__(self, type, value, traceback):
+    finish = timeit.default_timer()
+    self.time = finish - self.start
+
+@contextmanager
+def print_time(*args):
+  """
+  Measures and prints the time taken to execute nested code.
+  args: Additional arguments to print.
+  """
+  t = Timer()
+  print(*args)
+  with t:
+    yield
+  print(*args, end=' ')
+  print('finished in {0:.2f} second(s)'.format(t.time))