[Distutils] markers, <= and python 2.7.10

[Robert Collins]

So - 426 markers specify string comparisons only. This is now broken
in the wild :)

We need to figure out:
 - what comparisons we should allow (e.g. - versions, or tuples, or ?)
 - what the migration strategy for early adopters looks like
    - do we change the meaning of python_version
    - do we define a new symbol name
    - do we break existing markers, or force some type gymnastics
(e.g. casting the user side of the marker to a sequence of
components)?

https://bitbucket.org/pypa/setuptools/commits/e01e9a77fad5
https://github.com/pypa/pip/issues/2943

-Rob


-- 
Robert Collins <rbtcollins at hp.com>
Distinguished Technologist
HP Converged Cloud