Changed Result::get to return a const reference.

Review: https://reviews.apache.org/r/18434
Added stout/interval.hpp to model boost interval set.

Review: https://reviews.apache.org/r/18093
Updated Makefile.am for the new interval set tests.

Review: https://reviews.apache.org/r/18333
Added a verify-reviews.py script that can run via CI to verify
Review Board reviews.

Review: https://reviews.apache.org/r/18676/