Adds issues_tests for testing GitHub issues.

Adds rake task for explicitly running issues_tests, which do not get run
via `rake test`.

Adds failing test for #46. 

This PR does not resolve the issue, but I wanted to get some eyes on the `issues_tests` idea @bcardarella @danmcclain. Basically, if we're debugging an issue, I'd like to preserve the work we get to the bottom of the issue, rather than building temporary `foo` tests.