22720 - --nodes 'nodefile' doesn't work on ruby 1.9.3

In the past the nodes option failed on ruby 1.9.3 because the input
value was replacing the discovery_options array with a string.

This commit appends the input value to the discovery_options array and
adds some additional testing for the Optionparser class.
Merge pull request #113 from ploubser/bug/master/22720

22720 - --nodes 'nodefile' doesn't work on ruby 1.9.3