Updates gem dependencies, style rules

src/ruby/.rubocop_todo.yml

 # This configuration was generated by `rubocop --auto-gen-config`
-# on 2015-04-14 09:35:44 -0700 using RuboCop version 0.29.1.
+# on 2015-04-15 18:43:23 -0700 using RuboCop version 0.30.0.
 # The point is for the user to remove these configuration records
 # one by one as the offenses are removed from the code base.
 # Note that changes in the inspected code, or installation of new
@@ -9,7 +9,7 @@
 Metrics/AbcSize:
   Max: 36
 
-# Offense count: 2
+# Offense count: 3
 # Configuration parameters: CountComments.
 Metrics/ClassLength:
   Max: 183

src/ruby/grpc.gemspec

@@ -22,16 +22,16 @@ Gem::Specification.new do |s|
   s.platform      = Gem::Platform::RUBY
 
   s.add_dependency 'google-protobuf', '~> 3.0.0alpha.1.1'
-  s.add_dependency 'googleauth', '~> 0.4'
+  s.add_dependency 'googleauth', '~> 0.4'  # reqd for interop tests
   s.add_dependency 'logging', '~> 1.8'
   s.add_dependency 'minitest', '~> 5.4'  # reqd for interop tests
   s.add_dependency 'xray', '~> 1.1'
 
-  s.add_development_dependency 'bundler', '~> 1.7'
-  s.add_development_dependency 'rake', '~> 10.0'
-  s.add_development_dependency 'rake-compiler', '~> 0'
-  s.add_development_dependency 'rubocop', '~> 0.28.0'
-  s.add_development_dependency 'rspec', '~> 3.0'
+  s.add_development_dependency 'bundler', '~> 1.9'
+  s.add_development_dependency 'rake', '~> 10.4'
+  s.add_development_dependency 'rake-compiler', '~> 0.9'
+  s.add_development_dependency 'rubocop', '~> 0.30'
+  s.add_development_dependency 'rspec', '~> 3.2'
 
   s.extensions = %w(ext/grpc/extconf.rb)
 end