Require six for cross Python compatibility. Update imports for Python 3 compatibility.

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Prefer print_function for Python 3 compatibility

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Update another usage of ConfigParser for Python 3

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extra : rebase_source : d79b615c3d204e5b750a19f5bd198bed80fb4cd4
extra : histedit_source : 3bcd01d501f65d493fd62ccf3835542aaef51734
Use six.moves.range for Python 3 compatibility

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Use six for string type detection for improved Python 3 compatibility

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extra : histedit_source : af7c95e8be0cf664e7ab4363279d4c5324219d1d
Use six for text type for improved Python 3 compatibility

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Correct indentation
Merge pull request #304 from jaraco/working

Python 3 improvements