Include six copy and deprecates compat.
WIP: Update several modules to use six.
Merge branch 'develop' into with-six
Minor doc fix.
Provide test for `extract_attrs`.  Finds a BUG.
Fix bug with `extract_attrs`.
Fix bug with unicode paths in `get_traverser`. [py27]
Revert "Fix bug with unicode paths in `get_traverser`. [py27]"

This was actually fixed when `extract_attrs` was reimplemented with
get_traverser.
Mark the next version as 1.5.4.
Merge branch 'develop' into with-six

Conflicts:
	tests/test_metaclass.py
	xoutil/aop/classical.py
	xoutil/objects.py
Clean up more compat uses.
Notice deprecation of ``xoutil.compat``.
Fix spelling.
Merge branch 'develop' into release-1.5.4
Release 1.5.4.