Prevent Rouge 1.9.1 from matching gem requirements

It winds up loading the same file twice,
causing constants to be redefined,
which causes warnings to print every time it is run.
See rouge-ruby/rouge#296 for more details.

what_weve_got_here_is_an_error_to_communicate.gemspec

@@ -10,7 +10,7 @@ Gem::Specification.new do |s|
   s.files       = `git ls-files`.split("\n")
   s.homepage    = 'https://github.com/JoshCheek/what-we-ve-got-here-is-an-error-to-communicate'
 
-  s.add_runtime_dependency 'rouge', '~> 1.8'
+  s.add_runtime_dependency 'rouge', '~> 1.8', '!= 1.9.1'
 
   s.add_development_dependency 'rspec', '~> 3.2'
   s.add_development_dependency 'haiti', '< 0.3',  '>= 0.2.0'