Removes reference to removed function collect_unused_bases
Includes is_valid_public_identifier and docstrings
Includes validators docs
Updates the ChangeLog in the docs
Includes a tests for constructors double calling in Python 2.7 when using xoutil.objects.metaclass
Adds sphinx.ext.viewcode to ease studying of the code
Improves notices in Python 2.7's double calling of __new__ in xoutil.objects.metaclass
FIXME: Don't modify f_globals for annotation purposes
Fixes xoutil.aop.basic documentation by exposing the right signature