Replace the custom gem-related Rake tasks with Bundler's

Rakefile

@@ -1,25 +1,5 @@
+require "bundler/gem_tasks"
 require "rake/testtask"
-require "freno/client/version"
-
-# gem install pkg/*.gem
-# gem uninstall freno-client freno-throttler
-desc "Build gem into the pkg directory"
-task :build do
-  FileUtils.rm_rf("pkg")
-  Dir["*.gemspec"].each do |gemspec|
-    system "gem build #{gemspec}"
-  end
-  FileUtils.mkdir_p("pkg")
-  FileUtils.mv(Dir["*.gem"], "pkg")
-end
-
-desc "Tags version, pushes to remote, and pushes gem"
-task release: :build do
-  sh "git", "tag", "v#{Freno::Client::VERSION}"
-  sh "git push origin master"
-  sh "git push origin v#{Freno::Client::VERSION}"
-  sh "ls pkg/*.gem | xargs -n 1 gem push"
-end
 
 Rake::TestTask.new(:test) do |t|
   t.libs << "test"