Silence `have` matcher deprecation warnings within our specs.
Scope the `BagOfWords` classes so they don't redefine each other.
Avoid `useless use of == in avoid context` warning.

…by calling a method on the result.
It's a hack but it'll help us to keep rspec-expectations warning free.
Merge pull request #345 from rspec/silence-have-matcher-deprecations

Silence have matcher deprecations