Add linting support to cli

[sd416]

Output looks like

root@bdeb2ab2a999:/plugin# cd eta/
root@bdeb2ab2a999:/plugin/eta# /app/bin/trmnlp lint
1 issue found:

  1. Markup uses too many inline styles, add more native Framework classes.
     Learn more: https://help.trmnl.com/en/articles/11395668-recipe-best-practices#h_3a3eab0712

root@bdeb2ab2a999:/plugin/eta# 

This fixes #82

[sd416]

@schrockwell can you please take a look at this?