clones should not share an env dict

This is similar to #2, but I think more correct.

Previously, cloned commands were sharing a single ._env attribute.
Classes' _clone methods should ensure that there's a copy made of any mutable attributes, and Operation wasn't doing this for its _env dict.
Doesn't block the merge imo

--phone is hard.
On Oct 3, 2014 10:11 AM, "Mike Thornton" <notifications@github.com> wrote:

> In src/clom/command.py:
>
> > @@ -281,6 +281,7 @@ def _clone(self):
> >          q = cls.__new__(cls)
> >          q.__dict__ = self.__dict__.copy()
> >          q._redirects = self._redirects.copy()
> > +        q._env = self._env.copy()
>
> _pipe_to should be copied as well.
>
> —
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> <https://github.com/six8/python-clom/pull/4/files#r18406610>.
>