Start adding json input
Add basic nested support for json input
Use the schema for sub sheet names during json input
Add support for id fields in JSON input
Add the cli interface for flattening (json->spreadsheet)
Add tests for existing xlsx and csv output (ie. from scheam)
Add tests for lines output (ie. content from flattened JSON)
Implement lines output (ie. output spreadsheet content rows)
Fix flattening bug
Output extra columns from the schema upon flattening
Fix Python 2 support
Fix conversion for sample data

Add support for nulls
Don't require schema in CLI flattening interface
Don't add duplicate columns for arrays
Ensure id fields are not outputted on main sheet when flattening
Fix incorrectly nested id output