Use Ruby 2.2.9 on Travis again (#1552)

The test failures we saw after upgrading last time were caused by the
stopgap_13632 gem not being activated on the new version.

.travis.yml

@@ -11,7 +11,7 @@ branches:
   only:
     - "master"
 rvm:
-  - 2.2.8
+  - 2.2.9
   - 2.3.6
   - 2.4.3
   - 2.5.0

Gemfile

@@ -13,6 +13,6 @@ gem "jruby-openssl", :platform => "jruby"
 
 gem "rubocop", "~> 0.50.0"
 
-if %w(2.2.7 2.2.8 2.3.4 2.4.1).include? RUBY_VERSION
+if %w(2.2.7 2.2.8 2.2.9 2.3.4 2.4.1).include? RUBY_VERSION
   gem "stopgap_13632", "~> 1.0", :platforms => ["mri", "mingw", "x64_mingw"]
 end

README.md

@@ -217,10 +217,10 @@ Some platforms do not support all Puma features.
 
 ## Known Bugs
 
-For MRI versions 2.2.7, 2.2.8, 2.3.4 and 2.4.1, you may see ```stream closed in another thread (IOError)```. It may be caused by a [Ruby bug](https://bugs.ruby-lang.org/issues/13632). It can be fixed with the gem https://rubygems.org/gems/stopgap_13632:
+For MRI versions 2.2.7, 2.2.8, 2.2.9, 2.3.4 and 2.4.1, you may see ```stream closed in another thread (IOError)```. It may be caused by a [Ruby bug](https://bugs.ruby-lang.org/issues/13632). It can be fixed with the gem https://rubygems.org/gems/stopgap_13632:
 
 ```ruby
-if %w(2.2.7 2.2.8 2.3.4 2.4.1).include? RUBY_VERSION
+if %w(2.2.7 2.2.8 2.2.9 2.3.4 2.4.1).include? RUBY_VERSION
   begin
     require 'stopgap_13632'
   rescue LoadError

test/helper.rb

@@ -1,7 +1,7 @@
 # Copyright (c) 2011 Evan Phoenix
 # Copyright (c) 2005 Zed A. Shaw
 
-if %w(2.2.7 2.2.8 2.3.4 2.4.1).include? RUBY_VERSION
+if %w(2.2.7 2.2.8 2.2.9 2.3.4 2.4.1).include? RUBY_VERSION
   begin
     require 'stopgap_13632'
   rescue LoadError