Fix be_routable description -- Defines BeRoutableMatcher#description

[tonyta]

Alternate implementation of #1307
Thanks for the feedback @JonRowe @cupakromer! 😹

Problem
Previously, using be_routable in a one-liner...

RSpec.describe 'a not-routable route', type: :routing do
  let(:sad_route) { '/this/route/makes/me/sad' }
  specify { expect(get: sad_route).not_to be_routable }
end

...will output the following:

a not-routable route
  should not be routable matcher

BaseMatcher#description turns BeRoutableMatcher into "be routable matcher".

Solution
BeRoutableMatcher#description is defined to override BaseMatcher#description...

class BeRoutableMatcher < RSpec::Matchers::BuiltIn::BaseMatcher
  # ...
  def description
    "be routable"
  end
end

...to correctly output:

a not-routable route
  should not be routable

[JonRowe]

Thanks @tonyta

[tonyta]

Thanks, @JonRowe! Happy to help! 🐙