Test on Rails 5.2 & fix mysql for older Rails

.travis.yml

@@ -2,14 +2,17 @@ cache: bundler
 sudo: false
 language: ruby
 rvm:
-  - 2.4.0
-  - 2.3.3
-  - 2.2.7
+  - 2.6.0
+  - 2.5.0
+  - 2.4.3
+  - 2.3.6
+  - 2.2.9
 # these haven't been passing for a while:
 #  - jruby-head
 #  - rbx
 
 gemfile:
+  - gemfiles/activerecord_5.2.gemfile
   - gemfiles/activerecord_5.1.gemfile
   - gemfiles/activerecord_5.0.gemfile
   - gemfiles/activerecord_4.2.gemfile
@@ -27,3 +30,4 @@ matrix:
     - gemfile: gemfiles/activerecord_edge.gemfile
     - rvm: jruby-head
     - rvm: rbx
+    - rvm: 2.6.0

gemfiles/activerecord_4.2.gemfile

@@ -5,7 +5,7 @@ source "https://rubygems.org"
 gem "activerecord", "~> 4.2.0"
 
 platforms :ruby, :rbx do
-  gem "mysql2"
+  gem "mysql2", '~> 0.4.10'
   gem "pg", '~> 0.21.0'
   gem "sqlite3"
 end

gemfiles/activerecord_5.0.gemfile

@@ -5,7 +5,7 @@ source "https://rubygems.org"
 gem "activerecord", "~> 5.0.0"
 
 platforms :ruby, :rbx do
-  gem "mysql2"
+  gem "mysql2", '~> 0.4.10'
   gem "pg", '~> 0.21.0'
   gem "sqlite3"
 end

gemfiles/activerecord_5.1.gemfile

@@ -5,7 +5,7 @@ source "https://rubygems.org"
 gem "activerecord", "~> 5.1.0"
 
 platforms :ruby, :rbx do
-  gem "mysql2"
+  gem "mysql2", '~> 0.4.10'
   gem "pg"
   gem "sqlite3"
 end

gemfiles/activerecord_5.2.gemfile

@@ -0,0 +1,19 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "rails", '~> 5.2.0.rc2'
+
+platforms :ruby, :rbx do
+  gem "mysql2", '~> 0.4.10'
+  gem "pg"
+  gem "sqlite3"
+end
+
+platforms :jruby do
+  gem "activerecord-jdbcmysql-adapter"
+  gem "activerecord-jdbcpostgresql-adapter"
+  gem "activerecord-jdbcsqlite3-adapter"
+end
+
+gemspec :path => "../"