Fix the intermittent test: `missing attribute:: scope 1`
Fix the intermittent test: `missing attribute:: scope 1`

Reset all cached information about columns after defining the model to prevent old columns from leaking for other tests.

e.g.: https://travis-ci.org/thoughtbot/shoulda-matchers/jobs/622356910

thoughtbot/shoulda-matchers,biow0lf/shoulda-matchers,biow0lf/shoulda-matchers,thoughtbot/shoulda-matchers,biow0lf/shoulda-matchers,reacuna/shoulda-matchers,thoughtbot/shoulda-matchers,thoughtbot/shoulda-matchers,reacuna/shoulda-matchers,biow0lf/shoulda-matchers,reacuna/shoulda-matchers,reacuna/shoulda-matchers