Add mute as development dependency

Author: Chris Hunt

github-auth.gemspec

@@ -22,6 +22,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'cane',           '~> 2.6.1'
   spec.add_development_dependency 'cane-hashcheck', '~> 1.2.0'
   spec.add_development_dependency 'coveralls',      '~> 0.7.0'
+  spec.add_development_dependency 'mute',           '~> 1.0.0'
   spec.add_development_dependency 'pry',            '~> 0.9.12.4'
   spec.add_development_dependency 'rake',           '~> 10.1.1'
   spec.add_development_dependency 'rspec',          '~> 2.14.1'