v2.12.2

• Fix crashing bug in the _doc command.
• Dropped official support for 1.8.7. This version of Ruby is long-deprecated and while GLI should continue to work, the tools needed to develop GLI exhibit strange behavior that cause tests to fail. Rather than lock to older versions of the tools or waste time figuring out the problem, I've removed 1.8.7 from .travis.yml. I don't plan to introduce 1.9 or 2.0-only code to GLI, but am not going to spend time making sure it works on 1.8.7