Merge remote-tracking branch 'laurentb/dev-python/pytest-xdist'

Merge remote-tracking branch 'laurentb/dev-python/pytest-xdist'

Add DOCS and a missing Setuptools DEPEND.

I've dropped LICENSE from his DOCS because its content matches the
wording used by the Open Source Initiative [1].  It also matches the
wording used by the MIT license in the gentoo tree, although that one
has an additional:

  [Except as contained in this notice ...]

block at the end.

[1]: http://opensource.org/licenses/MIT