Only support Rails 4.2 and 5. Remove foreigner

.travis.yml

@@ -3,16 +3,19 @@ cache: bundler
 sudo: false
 
 rvm:
-  - 2.0
   - 2.1.10
   - 2.2.5
   - 2.3.1
 
 gemfile:
-  - gemfiles/rails3.2.gemfile
-  - gemfiles/rails4.0.gemfile
-  - gemfiles/rails4.1.gemfile
   - gemfiles/rails4.2.gemfile
+  - gemfiles/rails5.0.gemfile
+
+matrix:
+  exclude:
+    - rvm: 2.1.10
+      gemfile: gemfiles/rails5.0.gemfile
+
 env:
   global:
     - NOKOGIRI_USE_SYSTEM_LIBRARIES=true

Appraisals

@@ -1,11 +1,3 @@
-appraise "rails3.2" do
-  gem "rails", "~> 3.2.21"
-end
-
-appraise "rails4.0" do
-  gem "rails", "~> 4.0.13"
-end
-
-appraise "rails4.1" do
-  gem "rails", "~> 4.1.13"
+appraise "rails4.2" do
+  gem "rails", "~> 4.2.6"
 end

gemfiles/rails5.0.gemfile

@@ -0,0 +1,7 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "rails", "~> 5.0.0"
+
+gemspec path: "../"

lib/mailboxer/engine.rb

@@ -1,5 +1,3 @@
-# Database foreign keys
-require 'foreigner' if Rails.version < "4.2.0"
 require 'carrierwave'
 begin
   require 'sunspot_rails'

mailboxer.gemspec

@@ -20,11 +20,9 @@ Gem::Specification.new do |s|
 
   # Gem dependencies
   #
-  # SQL foreign keys
-  s.add_runtime_dependency('foreigner', '>= 0.9.1')
 
   # Development Gem dependencies
-  s.add_runtime_dependency('rails', '>= 3.2.0')
+  s.add_runtime_dependency('rails', '>= 4.2.0')
   s.add_runtime_dependency('carrierwave', '>= 0.5.8')
 
   if RUBY_ENGINE == "rbx" && RUBY_VERSION >= "2.1.0"