Revert "Merge pull request #891 from lukecampbell/validate_unit"

This reverts commit 07682c121bb2ec9eb511d8abde1e07a75c02d183, reversing
changes made to a14ee948b867ee42df6cad117a79812b3c4e9a81.
Revert "Adds udunitspy to setup.py"

This reverts commit 0da6e3be9427c33450214861c14e470658cff1b8.
Merge pull request #916 from lukecampbell/reverts

Reverts