add Rails 5.1 and 5.2 appraisals

.travis.yml

@@ -4,6 +4,8 @@ cache: bundler
 
 gemfile:
   - gemfiles/rails_5_0.gemfile
+  - gemfiles/rails_5_1.gemfile
+  - gemfiles/rails_5_2.gemfile
 
 rvm:
   - "2.5.1"

Appraisals

@@ -1,3 +1,11 @@
 appraise "rails_5_0" do
   gem "rails", "~> 5.0.0"
+end
+
+appraise "rails_5_1" do
+  gem "rails", "~> 5.1.0"
+end
+
+appraise "rails_5_2" do
+  gem "rails", "~> 5.2.0"
 end

gemfiles/rails_5_1.gemfile

@@ -0,0 +1,18 @@
+# This file was generated by Appraisal
+
+source "http://rubygems.org"
+
+gem "rails", "~> 5.1.0"
+gem "rspec"
+gem "rspec-rails", "~> 3.7"
+gem "timecop"
+gem "byebug"
+gem "appraisal"
+gem "sqlite3"
+gem "nokogiri", "~> 1.8"
+
+group :active_record do
+  gem "sqlite3-ruby", require: "sqlite3"
+end
+
+gemspec path: "../"

gemfiles/rails_5_2.gemfile

@@ -0,0 +1,18 @@
+# This file was generated by Appraisal
+
+source "http://rubygems.org"
+
+gem "rails", "~> 5.2.0"
+gem "rspec"
+gem "rspec-rails", "~> 3.7"
+gem "timecop"
+gem "byebug"
+gem "appraisal"
+gem "sqlite3"
+gem "nokogiri", "~> 1.8"
+
+group :active_record do
+  gem "sqlite3-ruby", require: "sqlite3"
+end
+
+gemspec path: "../"