Gemfile: Add "rake", rather than rely on it being present.
Gemfile: Add "rake", rather than rely on it being present.

DynamoMTL/spree_paper_trail_manager,justinrcook/paper_trail_manager,justinrcook/paper_trail_manager,reidab/paper_trail_manager,fusion94/paper_trail_manager,fusion94/paper_trail_manager,xinminlabs/paper_trail_manager,fusion94/paper_trail_manager,xinminlabs/paper_trail_manager,DynamoMTL/spree_paper_trail_manager,xinminlabs/paper_trail_manager,reidab/paper_trail_manager