Ignore comment lines.
Use singleton class on 1.9 rather than `class <<` syntax.
Convert a module extension to inclusion.

extend blows the method cache, so it's better
to include once at file load time.
Prefer `include` to `extend`.

Practically, it doesn't matter here, but since our
`method_cache_busters` script looks for uses of
`extend` this creates one less spot to ignore and
the `include` works just fine.
Add some more ignores.
Prevent new method cache busters from being added.
Merge pull request #1178 from rspec/remove-cache-busters-part-2

Remove cache busters part 2