Update gemspec

Rakefile

@@ -1,10 +1,10 @@
-require "bundler/gem_tasks"
-require "rake/testtask"
+require 'bundler/gem_tasks'
+require 'rake/testtask'
 
 Rake::TestTask.new(:test) do |t|
-  t.libs << "test"
-  t.libs << "lib"
-  t.test_files = FileList["test/**/*_test.rb"]
+  t.libs << 'test'
+  t.libs << 'lib'
+  t.test_files = FileList['test/**/*_test.rb']
 end
 
-task :default => :test
+task default: :test