Add RSpec dependency and configuration

.rspec

@@ -0,0 +1,2 @@
+--color
+--format progress

rack-canonical-host.gemspec

@@ -8,4 +8,5 @@ Gem::Specification.new do |gem|
   gem.files = Dir['LICENSE', 'README.rdoc', 'lib/**/*']
 
   gem.add_dependency 'rack', '>= 1.0.0'
+  gem.add_development_dependency 'rspec', '~> 2.0'
 end

spec/spec_helper.rb

@@ -0,0 +1,11 @@
+# This file was generated by the `rspec --init` command. Conventionally, all
+# specs live under a `spec` directory, which RSpec adds to the `$LOAD_PATH`.
+# Require this file using `require "spec_helper.rb"` to ensure that it is only
+# loaded once.
+#
+# See http://rubydoc.info/gems/rspec-core/RSpec/Core/Configuration
+RSpec.configure do |config|
+  config.treat_symbols_as_metadata_keys_with_true_values = true
+  config.run_all_when_everything_filtered = true
+  config.filter_run :focus
+end