remove commented chunk.
Stable import for byte-type and unicode-type.
Drop support for the mode parameter to TempDirectory.read().

I don't think anyone was using this, and we'll need to find a better solution if the line ending thing turns out to be important.
Drop the ancient path=True parameter.
Scrap these old doctests, we'll make sure we get coverage elsewhere if it's missing.
Comment noting why there are 2 fewer tests on PY3
more path param dropping.
Introduce proper handling of bytes versus strings when reading and writing files with TempDirectory.