I propose adding a command line `--minify` flag to the json/tool.py module. 

This flag, if specified, uses `indent=None` and `separators=(',', ':')` to eliminate indent and separator whitespace in the output.

Minifying JSON (as is also done frequently with JS, CSS, and sometimes HTML) is common practice, and would be useful to have as a command-line tool rather than a user needing to use an online resource to do so.