The Python datetime module is available on all supported platforms. The
types are always available and never raise an ImportError.

    ag -l Copyright | xargs sed -i \
        "s/\(.*copyright (C) [0-9]\+\)\(-[0-9]\+\)\?\(.*\)/\1-$(date +%Y)\3/I"

Allow returning unparsed bytes from databases with mixed encodings. See
issue #519.

I'm still fought whether docs should be in the C module or in the .rst.
I'd prefer the first because DRY, but writing multiline strings in C
really sucks.

Make all library code compatible with both Python 2 and Python 3. Helps
move to modern Python idioms. Can now write for Python 3 (with
workarounds for Python 2) instead of the other way around.

In the future, when it is eventually time to drop Python 2, the library
will be in a better position to remove workarounds

Added a very small comparability module compat.py where required. It
includes definitions for:

- text_type -- A type. str on Python 3. unicode on Python 2.
- string_types -- A tuple. Contains only str on Python 3. Contains str &
                  unicode on Python 2.