Improve test module discovery

Accept both `test_*.py` and `*_test.py` as valid test modules patterns.

Fix #135

docs/index.rst

@@ -306,10 +306,8 @@ Appendix
 Python Test Modules
 +++++++++++++++++++
 
-All files which match the following criteria:
-
-- file names start with ``test_``
-- file extension matches ``.py``
+All files which match the patterns ``test_*.py`` and ``*_test.py`` are
+considered Python test modules.
 
 Python Test case functions
 ++++++++++++++++++++++++++

testimony/__init__.py

@@ -4,6 +4,7 @@
 
 import ast
 import collections
+import fnmatch
 import itertools
 import json
 import os
@@ -57,7 +58,10 @@ def prefixed_lines():
 
 def is_test_module(filename):
     """Indicate if ``filename`` match a test module file name."""
-    return filename.startswith('test_') and filename.endswith('.py')
+    for pat in ('test_*.py', '*_test.py'):
+        if fnmatch.fnmatch(filename, pat):
+            return True
+    return False
 
 
 class TestFunction(object):