tests: Change assertEquals to be py3k compatible assertEqual.

Signed-off-by: Jelmer Vernooĳ <jelmer@samba.org>
Add dulwich.greenthreads module.
Remove pylint config.
Add 'flakes' target invoking pyflakes, and fix some pyflakes warnings.
Add pep8 make target and fix some pep8ness.
Stop using more deprecated test methods.
Use for loop instead of map.
Check for bytes rather than str.
Use bytes literals instead of string literals.