Maybe allow a few more obvious shorthands for semver specs

[bitprophet]

Spinoff of #45.

Noticed that e.g. in a situation where one puts out a minor release and major release at the same time, one doesn't actually want features in the minor to duplicate into the major all the time - it's implied the major will include them.

So, one wants to do e.g. (>=1.17,<2.0), explicitly. However, as it's a feature and thus only subject to landing in the one minor release bucket, one can more succinctly say (==1.17).

Thus this ticket is for making that even easier and perhaps allowing (1.17), i.e. the == is implicit. Not 100% sure, and assuming folks will only really want to use these syntaxes around (rare) major releases, it's not like we really need the savings. But noting just in case.