Only warn for mis-versioned packages.

Allows Package==dev in requirements.
Moved configuration and logging to .config for XDG compliance
Fixed commit #1 to actually work
Switched to use XDG_CONFIG_DIR environment variable if possible (default to ~/.config if not)
Added migration path from ~/.pip to ~/.config/pip
Minor fixes
Merged with upstream
Re-add import shutil that got lost in merge
Documented change and added author
Correct a comment
Add `mock` requirement
Ensure that $TMPDIR exists before running tests

This is normally done by TestFileEnvironment if the `start_clear` parameter is True,
but TestPipEnvironment and FastTestPipEnvironment explicitly set it to False.
Fix unicode tests to work with new temp file assertions
Add a test to ensure that the temp build dir is always removed
Remove temp build dir even if the req is not installed (fixes #420)
Minor tweak to handle not passing options to parse_requirements.

Options is supposed to be an optional argument, this makes it optional.
Update AUTHORS.txt
assert_no_temp feature tests
Fix test on windows CI
Issue #557 fix test failing on windows.

More path equality fun, use normpath to ensure path sep correct.