Should each release only have ONE gemfile for rails it supports?

[zenspider]

I'm trying to figure this out in order to get out a release but I'm operating in a bit of a vacuum here.

If the answer is yes, why do we have a matrix in the CI for multi version testing at all?

If the answer is no, what should I be doing extra to release?

I guess the real request here is for a DEPLOYING or CONTRIBUTING document.