Improve TAP compliance in test suite

This allows tools like `prove` to operate on our test-suite, allowing us
to do things like run recently-failing tests first, randomising test
order, and fancier reporting options.

Changes made:

- TAP output always goes to STDOUT, never to STDERR
- Skipped tests signaled as `ok 1 # skip` as per standard
- Expected failures signaled as `not ok 1 # TODO` as per standard
- `.prove` added to .gitignore

test/simpletap/__init__.py

@@ -155,12 +155,12 @@ class TAPTestResult(unittest.result.TestResult):
         if status:
 
             if status == "SKIP":
-                self.stream.writeln("{0} {1} - {2}: {3}".format(
-                    color("skip", "yellow"), self.testsRun, filename, desc)
+                self.stream.writeln("{0} {1} - {2}: {3} # skip".format(
+                    color("ok", "yellow"), self.testsRun, filename, desc)
                 )
             elif status == "EXPECTED_FAILURE":
-                self.stream.writeln("{0} {1} - {2}: {3}".format(
-                    color("skip", "yellow"), self.testsRun, filename, desc)
+                self.stream.writeln("{0} {1} - {2}: {3} # TODO".format(
+                    color("not ok", "yellow"), self.testsRun, filename, desc)
                 )
             else:
                 self.stream.writeln("{0} {1} - {2}: {3}".format(
@@ -227,6 +227,10 @@ class TAPTestRunner(unittest.runner.TextTestRunner):
         unittest.signals.registerResult(result)
         result.failfast = self.failfast
 
+        # TAP requires output is on STDOUT.
+        # TODO: Define this at __init__ time
+        result.stream = unittest.runner._WritelnDecorator(sys.stdout)
+
         with warnings.catch_warnings():
             if getattr(self, "warnings", None):
                 # if self.warnings is set, use it to filter all the warnings