Preserve the order of parameterized arguments

[paw-lu]

Parameterized jobs will now display in the same order as they are written.

"""Example noxfile.py"""
import nox

@nox.session()
@nox.parameterize(
  ("z", "a"),
  [
    (1, 2),
    (3, 4),
  ]
)
def job(z, a):
    ...

Before

% nox --list

* job(a=2, z=1)
* job(a=4, z=3)

After

% nox --list

* job(z=1, a=2)
* job(z=3, a=4)

Closes #264

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Thanks for the great library!

[cjolowicz]

LGTM

[theacodes]

Thank you!!!