Make all pin* methods behave conventionally the same

[radiantshaw]

Please read #66 and #67 to know the background behind why this PR is raised.

This PR replaces pin_all_from with pin_under which has the same thinking behind it as the pin method. Moreover, the pin_under method utilizes the Rails.application.config.assets.paths to figure out the files needed to be pinned, so that one does not have to specify the folder name from the Rails' root.

There's one thing which is remaining, that is when you specify just the folder name to pin_all_from:

pin_all_from "app/assets/javascripts"

it will pin all the files inside the app/assets/javascripts folder automatically, which I'm not sure how to do so with pin_under; so any and all suggestions are welcome. My idea was to have another method called pin_all which will only take one parameter, e.g. "app/assets/javascript" (from the Rails' root), and will do the job of pinning everything under that folder.

Also, feel free to suggest any changes and I'll be more than happy to do so.

[dhh]

Appreciate the work on this, but we're not going to change the API now. But I would take a PR that more clearly explained how what we have now works, based on your understanding 👍

[radiantshaw]

@dhh Sure. I can work on updating the documentation. But just out of curiosity, is there any plan for updating the API in future versions? Maybe we can keep the pin_all_from method and just do an addition to the existing API with pin_under?

Please note that this is in no way an intention to force merge code which you don't want to do. But I'm just curious about the roadmap and how the package should evolve.

[dhh]

No worries. I didn't find the proposed API simpler, tbh. Possible I'm just thinking of it a different way. But I don't see us changing this going forward at the moment.