• Deprecate whitelist/blacklist in favor of safelist/blocklist. (#181,
  thanks @renee-travisci). To upgrade and fix deprecations, find and replace instances of whitelist and blacklist with safelist and blocklist. If you reference rack.attack.match_type, note that it will have values like :safelist/:blocklist.
• Remove test coverage for unsupported ruby dependencies: ruby 2.0, activesupport 3.2/4.0, and dalli 1.
• Document example for setting X-RateLimit-* response headers (#193)