Add newer rubies to CI matrix

[mjankowski]

No description provided.

[jtdowney]

Thanks!

[mjankowski]

No prob ... unrelated to CI mix ... would you be open to a README PR cataloging the set of "what checks is the gem giving you beyond what ruby could be doing?" sort of thing...?

I believe the gem pre-dates the existence of private? (and maybe link_local? and loopback? as well?) in ruby itself -- it maybe be useful to see a quick venn diagram sort of look at whether you need the additional ranges from the CIDR list in the gem vs whatever core ruby covers.

And maybe to confirm before I do that ... are there still valid use cases in newer rubies, or would a README change like "In rubies newer than X you can just use methods x/y/z directly to gain the gem functionality" be appropriate?

(I am doing sort of a "lets review gems being used which have not had releases in years" sort of audit...)

[jtdowney]

I am open to reviewing PRs, although I no longer work in Ruby security daily. Relying on Ruby's predicate methods instead of maintaining CIDR lists is probably a good idea. Even in newer Rubies, I would expect parts of this gem (specifically the TCPSocket monkey patch) to be useful because you don't know what DNS names resolve until you resolve them and open the connection. For the general private address predicates, it is likely duplicative of the built-in methods.