Prepare for version 0.0.3.
Update Rake version.
Separate Compatibility constant definitions to its own file.
Alternate implementation of Compatibility.
Revert "Alternate implementation of Compatibility."

This reverts commit 00b74f0682ae45998e884d39e535f0f99a2ac8bb.
Revert "Separate Compatibility constant definitions to its own file."

This reverts commit 959ed0fbf430c27edd7984110b02290b280b8de7.
Yet another attempt at reducing Compatibility complexity outside of method definitions.
Revert code back.