Allow use of setuptools

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extra : rebase_source : 462b33ecd3f478a5a5b15c32e104a0fea34de66e
As Python 2.6 is now the minimum version requirement for jsonpickle, the checks for a required JSON module will always pass on the first check (grabbing the stdlib json module). Therefore, the checks have been removed.

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extra : rebase_source : bda28596800769c955878d8ea91351f1f7ee9a3c
Use Trove Classifiers to reflect supported Python versions in metadata.

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extra : rebase_source : 553a99d9e182a030c2033a5f4dd0c2b67e0c2fbc
Merge pull request #43 from jaraco/setup-script

Setup script cleanup