remove the String#== override

I moved it to the spec helper as suggested, to help make specs easier to
write.
add ErrorMessage#as_json
Merge pull request #2 from codekitchen/remove_core_ext

remove the String#== override
Merge pull request #3 from codekitchen/error_message_as_json

add ErrorMessage#as_json
bump version
bump version
Merge remote-tracking branch 'upstream/master' into rails2.3