Update null log handling for py26
Update null log handling for py26

Python 2.6 does not have a NullHandler in the logging
module, so introduce a little class that does the same
work.

Also add __all__ to the package init so extra names are
not exported.

Resolves issue #2

Change-Id: Id59d394cd02372e2c31de336894f06653cb1e22d

varunarya10/stevedore,openstack/stevedore,mandeepdhami/stevedore,JioCloud/stevedore,nelsnelson/stevedore,varunarya10/stevedore,citrix-openstack-build/stevedore,citrix-openstack-build/stevedore,mandeepdhami/stevedore,nelsnelson/stevedore,JioCloud/stevedore