Eliminate ruby warnings

Eliminates various warnings issues by ruby in its verbose warning mode (`ruby -w`, or `$VERBOSE = true`, or `RSpec.config.warnings = true`).

This was an issue for me in an app that I'm testing using `RSpec.config.warnings = true` (as recommended by the default RSpec generator); there are only a few warnings due to Timecop, but they get repeated *many* times.