Update version; fix dependency advisory comment

src/ruby/grpc.gemspec

@@ -14,7 +14,7 @@ Gem::Specification.new do |s|
   s.license       = 'BSD-3-Clause'
 
   s.required_ruby_version = '>= 2.0.0'
-  s.requirements << 'libgrpc ~> 0.6.0 needs to be installed'
+  s.requirements << 'libgrpc ~> 0.9.1 needs to be installed'
 
   s.files         = `git ls-files`.split("\n")
   s.test_files    = `git ls-files -- spec/*`.split("\n")

src/ruby/lib/grpc/version.rb

@@ -29,5 +29,5 @@
 
 # GRPC contains the General RPC module.
 module GRPC
-  VERSION = '0.9.2'
+  VERSION = '0.9.3'
 end