Support down-conversion to JSON

[tgregg]

The JSON down-conversion API was removed in #80 due to bugs identified in its implementation as documented in #67.

Functioning JSON down-conversion support should be added and exposed to users as an option on the text writer.

[aurghob33]

Hi - will this be taken up? If not, is there any guideline or template besides the cookbook based on which the downconversion can be implemented ?

[therapon]

There is a section in the cookbook that outlines the steps in English

http://amzn.github.io/ion-docs/guides/cookbook.html#down-converting-to-json

[tgregg]

The rules defined in the cookbook are authoritative and should be used when implementing this feature.

We don't have immediate plans to take this up, but we would welcome a contribution.