Doc [true, false] instead of [Boolean]
Remove tests for Chef 11.12.0
Move ChefSpec::Runner to ChefSpec::SoloRunner
Add ChefSpec::ServerRunner
Deprecate ChefSpec::Runner methods

ChefSpec::Runner.new has been replaced with either
ChefSpec::SoloRunner.new or ChefSpec::ServerRunner.new. 
ChefSpec::Runner.define_runner_method has been replaced by
ChefSpec.define_matcher.

The define_matcher helper does not dynamically define new methods on
the runner object. Instead, matchers are put into a hash and then
looked up by the ChefSpec::Runner implementation at runtime.
Replace deprecated methods in examples

- ChefSpec::Runner -> ChefSpec::SoloRunner
- ChefSpec::Runner.define_runner_method -> ChefSpec.define_matcher
Update features and examples to use the new ChefSpec::ServerRunner
Require a higher version of Chef
Test more recent Chef versions
Update README.md with modern practices and new Runner objects
Relax the constraint on Chef
Add deprecations for ChefSpec::Server