Put Gemfile for sub-directory of pubsub

examples/ruby/greeter*.rb and examples/ruby/route_guide/*.rb doesn't
need to depends on googleauth

examples/ruby/grpc-demo.gemspec

@@ -18,7 +18,6 @@ Gem::Specification.new do |s|
   s.platform      = Gem::Platform::RUBY
 
   s.add_dependency 'grpc', '~> 1.0'
-  s.add_dependency 'googleauth', '>= 0.5.1', '< 0.7'
 
   s.add_development_dependency 'bundler', '~> 1.7'
 end

examples/ruby/pubsub/.gitignore

@@ -0,0 +1,15 @@
+/.bundle/
+/.yardoc
+/Gemfile.lock
+/_yardoc/
+/coverage/
+/doc/
+/pkg/
+/spec/reports/
+/tmp/
+*.bundle
+*.so
+*.o
+*.a
+mkmf.log
+vendor

examples/ruby/pubsub/Gemfile

@@ -0,0 +1,4 @@
+source 'https://rubygems.org/'
+
+gem 'grpc', '~> 1.0'
+gem 'googleauth', '>= 0.5.1', '< 0.7'