Before removing a command after Coffee 1.0, we should add deprecation logic

[vincenzopalazzo]

I've been thinking about this for a while, and I believe it would be useful to implement it.

When Coffee is out of beta (by the end of summer), we should support a way to deprecate a command before removing it.

This means that we need to consider establishing a process for deprecation, but we should spend some more time thinking about it.