Version 1.5.9 released
Bug fix release for not_supported_on guard
Summary of changes:
- Fixes the not_supported_on guard bug that prevented it from running on MRI 1.8/1.9.
- The not_supported_on, deviates_on, extended_on guards now raise an exception if passed :ruby.
See http://rubyspec.org/wiki/rubyspec/Guards for documentation on all the spec guards.

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