WIP rewrite.
Rename core_extensions to backwards.
Add tests for describe, description methods.
Implement more description stuff, symbols as metadata.
Add regression test.

Thanks to @jrochkind for the example failing test.
Rename MiniSpec to Minispec.
Test specs from README.md.
Add support for testing minitest 4.
Add CHANGELOG.
Change Describe to not keep an unnecessary hash.
Use .ruby-version instead of .rvmrc.
Use slightly more helpful regression test.
Remove use of __dir__.
Try to define __dir__.
Add some compatibility notes to README.
Use flipflop on readme.specs.
Merge branch 'rewrite'