Turnout is using an outdated Rack version

[Roman Vitruk]

As for now turnout.gemspec contains the following Rack dependency:

s.add_dependency('rack', '>= 1.3', '< 3')

However, according to Snyk, Rack version 2.* has known security vulnerabilities, such as Web Cache Poisoning.

Is it possible to update this Rack dependency to use version 3.0 and above?