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Relax dependency on joshcooper/powershell

This patch would make it so that we do not depend on a specific version
of joshcooper/powershell, since it is still pre 1.0.0.
Relax dependency on stdlib to 3.2.0

We do not actually use any features that are only in 4.1.0 and since it
is equivalent to 3.2.0, we should use that to be more inclusive.
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Merge pull request #5 from ghoneycutt/metadata

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