fix bundler version in gemspec

Author: e2

ruby_dep.gemspec

@@ -28,5 +28,5 @@ Gem::Specification.new do |spec|
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ['lib']
 
-  spec.add_development_dependency 'bundler', '~> 1.12.a'
+  spec.add_development_dependency 'bundler', '~> 1.11'
 end