Invalid JSON generated with NSNumbers storing Inf/NaN

I encountered an issue with the generated JSON sending values for infinity.   The Standard for JSON states that NaN and [+-]Inf are not supported.   Chrome appears to handle this fine, however many other JSON parsers are not happy with this and generate errors.  This fixes the behavior by returning a string for the invalid number values.   The behavior in the chrome debugger is identical, but the generated JSON is valid.