Proto3 enum value 0 does not display

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Create Proto3 enum, first element is required to be 0.
2. Populate the enum value with the first value of the enum. 'type=0' should be 
the result.
3. Json output will not output this value.

I expect the enum to output when set to the first enum value. Instead the 
element does not output at all. It's just missing.

I am using 'protobuf-java-format:1.2', Used on a unix based system (MAC)

Original issue reported on code.google.com by NickWei...@gmail.com on 30 Jul 2015 at 4:31