[WIP] Added test coverage

We're using trollop in a project and noticed that its test coverage wasn't 100%. Of course striving for perfection is silly, but I took a look at it, and quickly covered almost all the remaining cases. I also found two branches that were never taken (and if they were, would cause an exception), and removed them.

via [gitorius](https://gitorious.org/trollop/mainline/merge_requests/3)