Install Appraisal so we can test against multiple versions of Rack

.gitignore

@@ -2,3 +2,5 @@ Gemfile.lock
 *.gem
 tmp/
 stdout
+gemfiles/vendor
+gemfiles/*.gemfile.lock

.travis.yml

@@ -10,3 +10,7 @@ matrix:
   allow_failures:
     - rvm: jruby-head
     - rvm: ruby-head
+# Put this in your .travis.yml
+gemfile:
+  - gemfiles/rack_2.gemfile
+  - gemfiles/rack_1.gemfile

Appraisals

@@ -0,0 +1,7 @@
+appraise 'rack-2' do
+  gem 'rack', '~> 2'
+end
+
+appraise 'rack-1' do
+  gem 'rack', '~> 1'
+end

bin/appraisal

@@ -0,0 +1,17 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+#
+# This file was generated by Bundler.
+#
+# The application 'appraisal' is installed as part of a gem, and
+# this file is here to facilitate running it.
+#
+
+require "pathname"
+ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../../Gemfile",
+  Pathname.new(__FILE__).realpath)
+
+require "rubygems"
+require "bundler/setup"
+
+load Gem.bin_path("appraisal", "appraisal")

gemfiles/rack_1.gemfile

@@ -0,0 +1,7 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "rack", "~> 1"
+
+gemspec :path => "../"

gemfiles/rack_2.gemfile

@@ -0,0 +1,7 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "rack", "~> 2"
+
+gemspec :path => "../"

redis-rack.gemspec

@@ -28,5 +28,6 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'minitest', '~> 5'
   s.add_development_dependency 'redis-store-testing'
   s.add_development_dependency 'connection_pool',     '~> 1.2.0'
+  s.add_development_dependency 'appraisal'
 end