Update more dependencies, fix deprecations

Build is stable as of this version, but still unmaintained otherwise. No new feature development.

v1.2.0

Updating ruby to 2.6.x. Updating bundler and dependencies.

v1.1.5

• Upgrade dependencies
• Ruby 2.2 support

v1.1.3

• Ensure Rack protocol compliance

v1.1.2

• Performance optimization around very large IP sets