use rspec format documentation for CI (#289)

Author: toy

Rakefile

@@ -6,6 +6,7 @@ require "rspec/core/rake_task"
 
 RSpec::Core::RakeTask.new("test") do |t|
   t.ruby_opts = "-w"
+  t.rspec_opts = "--format=documentation" if ENV["CI"]
 end
 
 task default: :test