Add tests for Rails 5.2

Rails 5.2 is imminent so we should add support for it.

.travis.yml

@@ -18,6 +18,7 @@ gemfile:
   - gemfiles/rails42.gemfile
   - gemfiles/rails50.gemfile
   - gemfiles/rails51.gemfile
+  - gemfiles/rails52.gemfile
 matrix:
   allow_failures:
     - rvm: ruby-head
@@ -26,6 +27,8 @@ matrix:
       gemfile: gemfiles/rails50.gemfile
     - rvm: 2.1
       gemfile: gemfiles/rails51.gemfile
+    - rvm: 2.1
+      gemfile: gemfiles/rails52.gemfile
     - rvm: 2.4.1
       gemfile: gemfiles/rails40.gemfile
     - rvm: 2.4.1

Appraisals

@@ -21,3 +21,8 @@ end
 appraise 'rails51' do
   gem 'rails', '>= 5.1.0.rc1', '< 5.2'
 end
+
+appraise 'rails52' do
+  gem 'rails', '>= 5.2.0.beta2', '< 5.3'
+  gem 'mysql2', '~> 0.4.4'
+end

gemfiles/rails52.gemfile

@@ -0,0 +1,8 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "rails", ">= 5.2.0.beta2", "< 5.3"
+gem "mysql2", "~> 0.4.4"
+
+gemspec name: "audited", path: "../"