Test against latest ruby and rails (#161)

* Test against Rails 6.0.0.rc1
* Test against Ruby 2.6
* Use Bundler v1 on Travis CI

This change speeds up testing configuration for older Rails versions (< 5)
on Travis CI

Ref: https://docs.travis-ci.com/user/languages/ruby/#bundler-20

Allow Rails 3.2 to fail against Ruby 2.4, 2.5, and 2.6
Do not allow Rails 4.2 to fail against Ruby 2.4

Refs:
- https://github.com/rails/rails/blob/3-2-stable/.travis.yml#L28-L35
- https://github.com/rails/rails/blob/4-2-stable/.travis.yml#L25-L31

.travis.yml

@@ -1,8 +1,10 @@
 language: ruby
 before_install:
-  - gem install bundler
+  - gem uninstall -v '>= 2' -i $(rvm gemdir)@global -ax bundler || true
+  - gem install bundler -v '< 2'
 rvm:
   - ruby-head
+  - 2.6
   - 2.5
   - 2.4
   - 2.3
@@ -17,34 +19,55 @@ gemfile:
   - gemfiles/rails_5.gemfile
   - gemfiles/rails_5.1.gemfile
   - gemfiles/rails_5.2.gemfile
+  - gemfiles/rails_6.0.gemfile
 matrix:
   allow_failures:
     - rvm: ruby-head
+    - rvm: 2.4
+      gemfile: gemfiles/rails_3.gemfile
     - rvm: 2.4
       gemfile: gemfiles/rails_4.gemfile
     - rvm: 2.4
       gemfile: gemfiles/rails_4.1.gemfile
-    - rvm: 2.4
-      gemfile: gemfiles/rails_4.2.gemfile
+    - rvm: 2.5
+      gemfile: gemfiles/rails_3.gemfile
     - rvm: 2.5
       gemfile: gemfiles/rails_4.gemfile
     - rvm: 2.5
       gemfile: gemfiles/rails_4.1.gemfile
     - rvm: 2.5
       gemfile: gemfiles/rails_4.2.gemfile
+    - rvm: 2.6
+      gemfile: gemfiles/rails_3.gemfile
+    - rvm: 2.6
+      gemfile: gemfiles/rails_4.gemfile
+    - rvm: 2.6
+      gemfile: gemfiles/rails_4.1.gemfile
+    - rvm: 2.6
+      gemfile: gemfiles/rails_4.2.gemfile
   exclude:
+    - rvm: 2.4
+      gemfile: gemfiles/rails_6.0.gemfile
+    - rvm: 2.3
+      gemfile: gemfiles/rails_6.0.gemfile
+    - rvm: 2.2
+      gemfile: gemfiles/rails_6.0.gemfile
     - rvm: 2.1
       gemfile: gemfiles/rails_5.gemfile
     - rvm: 2.1
       gemfile: gemfiles/rails_5.1.gemfile
     - rvm: 2.1
       gemfile: gemfiles/rails_5.2.gemfile
+    - rvm: 2.1
+      gemfile: gemfiles/rails_6.0.gemfile
     - rvm: 2.0
       gemfile: gemfiles/rails_5.gemfile
     - rvm: 2.0
       gemfile: gemfiles/rails_5.1.gemfile
     - rvm: 2.0
       gemfile: gemfiles/rails_5.2.gemfile
+    - rvm: 2.0
+      gemfile: gemfiles/rails_6.0.gemfile
 addons:
   code_climate:
     repo_token: 294f0ec8183176c0259b75eb21b38414508616985a7b39fc48fec9dfcf40a52e

Appraisals

@@ -27,3 +27,7 @@ end
 appraise "rails-5.2" do
  gem "rails", "~> 5.2.0"
 end
+
+appraise "rails-6.0" do
+ gem "rails", "~> 6.0.0.rc1"
+end

gemfiles/rails_6.0.gemfile

@@ -0,0 +1,7 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "rails", "~> 6.0.0.rc1"
+
+gemspec path: "../"