Add appraisal config to Rails 6 beta 3.

Author: edmilton

Appraisals

@@ -13,3 +13,7 @@ end
 appraise "5.2" do
   gem "rails", "~> 5.2"
 end
+
+appraise "6.0" do
+  gem 'rails', '~> 6.0.0.beta3'
+end

gemfiles/6.0.gemfile

@@ -0,0 +1,9 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "appraisal"
+gem "codeclimate-test-reporter"
+gem "rails", "~> 6.0.0.beta3"
+
+gemspec path: "../"