Update tools to python3 (#85)

This updates the scripts in the tools directory to work with python3, python2
support is now deprecated.

The only significant API change is that the subprocess module works in bytes
instead of str, the rest are mainly style changes.
diff --git a/tools/test_runner.py b/tools/test_runner.py
index 3a3f459..d4459ef 100644
--- a/tools/test_runner.py
+++ b/tools/test_runner.py
@@ -41,7 +41,7 @@
 
   tests = output.split()
   for f in filters:
-    tests = filter(re.compile(f).search, tests)
+    tests = list(filter(re.compile(f).search, tests))
 
   return tests
 
@@ -51,6 +51,7 @@
                        stdout=subprocess.PIPE,
                        stderr=subprocess.STDOUT)
   p_out, p_err = p.communicate()
+  p_out = p_out.decode()
   rc = p.poll()
 
   if rc == 0: