allow bundler 2.0 to make travis pass

Author: ianfixes

arduino_ci.gemspec

@@ -28,7 +28,7 @@ Gem::Specification.new do |spec|
   spec.add_dependency "os", "~> 1.0"
   spec.add_dependency "rubyzip", "~> 1.2"
 
-  spec.add_development_dependency "bundler", "~> 1.15"
+  spec.add_development_dependency "bundler", "> 1.15"
   spec.add_development_dependency "keepachangelog_manager", "~> 0.0.2"
   spec.add_development_dependency "rspec", "~> 3.0"
   spec.add_development_dependency 'rubocop', '~>0.59.0'