Allow users to create Tools

:construction: :rotating_light: :construction_worker: :rotating_light: :construction:

This is current in progress, and it is kind of a beefy PR.

This introduces the `Tool`, a way for folks to share their various tools and plugins on Supermarket.

Trello card: https://trello.com/c/oV2dAj7h

The todos lives in the Trello card. :smile_cat: 
Yeah, that is not the intention. I am doing it with the `Tool.find` because this should eventually redirect to the tool show, not the user's tools list. We just do not have the tool show view yet. :smile_cat: It is cool to leave it this way since that will allow us to get to the tool?