Add an adapter to adapt StreamResult event streams into ExtendedTestResult.

This permits running existing tools like test runners and reporters with
StreamResult generating test runs adapting any unittest or testtools compatible
TestResult into a StreamResult.
Add StreamTagger, for tagging StreamResult events.
Fixed SyntaxError when installing via Python 3
Add a timestamping StreamResult.

This allows event generators to ignore the timestamp field, it can be added
into the stream - as long as it is before any buffering/queueing/blocking occur
it will be accurate enough.
Add a StreamResult safe for use in threaded/concurrent code.