Print json instead of python repr

[indigoviolet]

Thank you for this tool, it is super helpful.

The output of conda tree leaves looks like JSON, but is actually a stringified version of a Python list, and annoying to parse. I suggest either adding a --json option or even better just printing valid JSON.

[rvalieris]

yes, thats a good point. the print(list) is something I added very early on but haven't changed since but it should have been something simpler like one package per line. we could also add --json option too.

[rvalieris]

new version now prints one package per line, and a --json option prints proper json.