Integration testing against Ruby 2.6

.travis.yml

@@ -1,14 +1,14 @@
 sudo: false
 language: ruby
 rvm:
-  - 2.5.1
-  - 2.4.4
-  - 2.3.7
+  - 2.6
+  - 2.5
+  - 2.4
+  - 2.3
 gemfile:
   - gemfiles/graphql_1.8.gemfile
   - gemfiles/graphql_1.9.gemfile
 before_script:
-  - gem install bundler
   - curl -L https://codeclimate.com/downloads/test-reporter/test-reporter-latest-linux-amd64 > ./cc-test-reporter
   - chmod +x ./cc-test-reporter
   - ./cc-test-reporter before-build

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    graphql-cache (0.6.0)
+    graphql-cache (0.5.0)
       graphql (~> 1, > 1.8)
 
 GEM
@@ -51,7 +51,6 @@ PLATFORMS
 
 DEPENDENCIES
   appraisal
-  bundler (~> 2.0)
   codeclimate-test-reporter
   graphql-cache!
   mini_cache
@@ -63,4 +62,4 @@ DEPENDENCIES
   sqlite3
 
 BUNDLED WITH
- 2.0.1
+ 1.17.3

graphql-cache.gemspec

@@ -22,7 +22,6 @@ Gem::Specification.new do |s|
   s.required_ruby_version = '>= 2.2.0' # bc graphql-ruby requires >= 2.2.0
 
   s.add_development_dependency 'appraisal'
-  s.add_development_dependency 'bundler', '~> 2.0'
   s.add_development_dependency 'codeclimate-test-reporter'
   s.add_development_dependency 'mini_cache'
   s.add_development_dependency 'pry'