Fix intermittently failing specs.

These specs would fail when run in isolation but
would pass when run after other specs that used the
`match` and `include` matchers first (causing them
to be loaded). To make them consistently pass,
we need to get the matchers before manipulating
the load path to ensure they are already loaded.
Merge pull request #1810 from rspec/fix-spec-that-replace-the-load-path

Fix intermittently failing specs.