Fix complication loop error. Fixes #61

Fixing #59 created this complication error but didn't notice it until
updating to the latest Xcode clang. The problem was that other includes
pulled in Exception which itself pulls in Module_impl which tries to use
Exception before it's defined. So, the one case that Exception is used I
simply replaced with a straight std::runtime_error, as it's something
that's wrong at definition.
Fix tests that are failing with Apple clang 5

Oddly, in-line strings weren't matching the return values, I guess the
type generated wasn't exactly the same. Setting the explicit type fixes
the tests.
Change ruby tests to use minitest