Wrap module in a closure

Your strict mode declaration isn't wrapped in a closure, potentially forcing all modules in a concatenated build that includes this file into strict mode, which is no good! While most concat plugins have an option for automatic closure wrapping, it's still best practice to wrap it yourself to prevent polluting the global namespace. :)

I also updated the karma dependencies since there were peer dependency errors, but then realized there were no tests anyway, so I can take that change out if you'd like.