NEXUS-7608: Added "trials" for Rubygems

Trials are part of "modern ITs" that are meant to perform
some "series of steps" that have some special requirements
against OS it runs, and their goal is to excercise the
given feature. They are meant to be run manually, are not
part of feature builds or run by CI.
NEXUS-7608: read version from src, not have it hardwired
NEXUS-7608: Cleanup of class

That had no reason to be on itself.
MEXUS-7608: Applied comments
NEXUS-7608: More cleanup
Merge pull request #843 from sonatype/nexus-2.11.x-NEXUS-7608-rubygems-trials

NEXUS-7608: Rubygems trials