Fix #83: Catch errors during analysis, set 'unknown' version (rev 1)

Now if there are errors when running a query against a specified
polisher target, polisher will gracefully catch and set version
to 'unknown' for that target/pkg

Updates gem_dep_checker to handle this edge case, specs still
need tbd for version_checker

Updated to incorporate rubocop & review feedback
Merge pull request #84 from ManageIQ/clone_err

Fix #83: Catch errors during analysis, set 'unknown' version