Add a newline at the end of json files when writing them.
Add a newline at the end of json files when writing them.

This fixes the really irritating ping-pong of newline/nonewline when editing
json files with an editor, and with `yotta version` commands.

eyeye/yotta,stevenewey/yotta,ntoll/yotta,autopulated/yotta,ARMmbed/yotta,ntoll/yotta,autopulated/yotta,stevenewey/yotta,BlackstoneEngineering/yotta,BlackstoneEngineering/yotta,eyeye/yotta,ARMmbed/yotta