Replace deprecated rubygems/gempackagetask with package_task.

Don't specify rubygems_version - set when package created.
Specify files in lib/spec with globs.

Rakefile

@@ -14,7 +14,7 @@
 # limitations under the License.
 
 require 'rubygems'
-require 'rake/gempackagetask'
+require 'rubygems/package_task'
 require 'rubygems/specification'
 require 'date'
 require 'rspec/core/rake_task'
@@ -29,10 +29,9 @@ spec = Gem::Specification.new do |s|
   s.date = Time.now.strftime("%Y-%m-%d")
   s.description = %q{kafka-rb allows you to produce and consume messages using the Kafka distributed publish/subscribe messaging service.}
   s.extra_rdoc_files = ["LICENSE"]
-  s.files = ["LICENSE", "README.md", "Rakefile", "lib/kafka", "lib/kafka/batch.rb", "lib/kafka/consumer.rb", "lib/kafka/io.rb", "lib/kafka/message.rb", "lib/kafka/producer.rb", "lib/kafka/request_type.rb", "lib/kafka/error_codes.rb", "lib/kafka.rb", "spec/batch_spec.rb", "spec/consumer_spec.rb", "spec/io_spec.rb", "spec/kafka_spec.rb", "spec/message_spec.rb", "spec/producer_spec.rb", "spec/spec_helper.rb"]
+  s.files = ["LICENSE", "README.md", "Rakefile"] + ["lib/**/*.rb", "spec/**/*.rb"].flat_map { |g| Dir.glob(g) }
   s.homepage = %q{http://github.com/acrosa/kafka-rb}
   s.require_paths = ["lib"]
-  s.rubygems_version = %q{1.3.7}
   s.summary = %q{A Ruby client for the Kafka distributed publish/subscribe messaging service}
 
   if s.respond_to? :specification_version then