Add lots of things(including tests)

test/difference/difference.test.py

@@ -0,0 +1,6 @@
+import types,functools
+from tape import test
+from difference import difference
+def difference_test(t):
+    t.true(isinstance(difference, (types.BuiltinFunctionType, types.FunctionType, functools.partial)),'difference is a function')
+test('Testing difference',difference_test)