Support rack 2.

* Prepare test environment for both rack 1 and rack 2 on Travis.
  * Update .travis.yml.
    * Add "bundle list" in script section to check rack's version
      from Travis log page.
  * Update Gemfile for rack 2 test, and
    add gemfiles/Gemfile.rack-1 for rack 1 test.
    * Keep codeclimate-test-reporter version < 1.
      To supress deprecated warning temporary.
      Later update it to latest version.
    * Add gems to Gemfile for Thorfile.
    * Specify sinatra 2.0.0.rc2 version for rack 2 test.
  * Delete Gemfile.lock
* Fix test suite for Rack 2.x compatiblity.

.gitignore

@@ -1,7 +1,8 @@
 pkg
 doc
 coverage
-Gemfile.lock
+/Gemfile*.lock
 VERSION
 *.rbc
-.bundle
+*.swp
+/.bundle

.travis.yml

@@ -2,13 +2,19 @@ language: ruby
 sudo: false
 before_install:
   - which bundle || gem install bundler
+script:
+  - bundle list
+  - bundle exec rake
 rvm:
   - 2.2.7
   - 2.3.4
   - 2.4.1
   - ruby-head
   - jruby-9.1.8.0
   - jruby-head
+gemfile:
+  - Gemfile
+  - Gemfile.rack-1.x
 matrix:
   allow_failures:
     - rvm: ruby-head

Gemfile

@@ -1,8 +1,15 @@
 source 'https://rubygems.org'
 
-gem 'rspec'
-gem "rack"
-gem "sinatra"
+gemspec
+
+# Development dependency
 gem 'rake'
+gem 'rspec'
+# To use rack 2
+gem 'sinatra', '~> 2.0.0.rc2'
+# Keep version < 1 to supress deprecated warning temporary.
+gem 'codeclimate-test-reporter', '< 1', :require => false
 
-gem "codeclimate-test-reporter", group: :test, require: nil
+# For Thorfile. Run "bundle exec thor help" to see the help.
+gem 'thor'
+gem 'git'

Gemfile.rack-1.x

@@ -0,0 +1,13 @@
+source 'https://rubygems.org'
+
+gemspec
+
+# Runtime dependency
+gem 'rack', '< 2'
+
+# Development dependency
+gem 'rake'
+gem 'rspec'
+gem 'sinatra'
+# Keep version < 1 to supress deprecated warning temporary.
+gem 'codeclimate-test-reporter', '< 1', :require => false