Add support for Rails 6.0.0 on Travis

.travis.yml

@@ -29,8 +29,8 @@ rails_supported_versions:
   - &rails_5_1_jruby RAILS_VERSION=5.1 JRUBY_OPTS='--dev -J-Xmx1024M --debug'
   - &rails_5_2 RAILS_VERSION=5.2
   - &rails_5_2_jruby RAILS_VERSION=5.2 JRUBY_OPTS='--dev -J-Xmx1024M --debug'
-  - &rails_6_0 RAILS_VERSION=6.0.0.rc2
-  - &rails_6_0_jruby RAILS_VERSION=6.0.0.rc2 JRUBY_OPTS='--dev -J-Xmx1024M --debug'
+  - &rails_6_0 RAILS_VERSION=6.0
+  - &rails_6_0_jruby RAILS_VERSION=6.0 JRUBY_OPTS='--dev -J-Xmx1024M --debug'
   - &rails_master RAILS_VERSION=master
   - &rails_master_jruby RAILS_VERSION=master JRUBY_OPTS='--dev -J-Xmx1024M --debug'
 

Gemfile

@@ -1,6 +1,12 @@
 # frozen_string_literal: true
 
 source 'https://rubygems.org'
+
+git_source(:github) do |repo_name|
+  repo_name = "#{repo_name}/#{repo_name}" unless repo_name.include?('/')
+  "https://github.com/#{repo_name}.git"
+end
+
 #
 # Add a Gemfile.local to locally bundle gems outside of version control
 local_gemfile = File.join(File.expand_path('..', __FILE__), 'Gemfile.local')

test/adapter/json/transform_test.rb

@@ -56,9 +56,8 @@ module ActiveModelSerializers
 
         def test_transform_undefined
           mock_request(:blam)
-          result = nil
           assert_raises NoMethodError do
-            result = @adapter.serializable_hash
+            @adapter.serializable_hash
           end
         end
 

test/support/serialization_testing.rb

@@ -20,11 +20,11 @@ module SerializationTesting
   end
 
   def with_prepended_lookup(lookup_proc)
-    original_lookup = ActiveModelSerializers.config.serializer_lookup_cahin
+    original_lookup = ActiveModelSerializers.config.serializer_lookup_chain
     ActiveModelSerializers.config.serializer_lookup_chain.unshift lookup_proc
     yield
   ensure
-    ActiveModelSerializers.config.serializer_lookup_cahin = original_lookup
+    ActiveModelSerializers.config.serializer_lookup_chain = original_lookup
   end
 
   # Aliased as :with_configured_adapter to clarify that