updated i18n to 0.5.0 to fix #1878

I'd have added a unit test to prove that this fixed the `objectNotation` bug, ala #1878 but I couldn't work out how to add data to the locales being tested without also forking and patching the `sails-generate-backed` project.

I have run the tests against this change however and nothing broke, so at least it's no worse than it was.