Bump Minitest dependency

This new version has an enhancement for the spec DSL's addl_description.
Update spec_type registration

Before Minitest 5.4 there was no addl argument sent to the blocks.
In 5.4 the splatted additional_desc values are sent.
Upgrade our spec_type blocks to accept the splatted addl desc values.
And fix the tests by removing the array on them. I dunno what I was thinking...