Run standardrb on Travis CI to verify the codebase conforms to the style guide

.standard.yml

@@ -2,6 +2,8 @@
 # For backwards compatilibity and idiosyncratic preferences of the main author,
 # there are some minor differences listed in here.
 
+ruby_version: 2.2
+
 ignore:
 - lib/chunky_png/**/*.rb:
   # We allow `for` loops in the codebase, especially in hot paths,

.travis.yml

@@ -1,5 +1,8 @@
 language: ruby
-script: bundle exec rake
+
+script:
+- bin/rake
+- bin/standardrb
 
 rvm:
 - "2.2"

bin/standardrb

@@ -0,0 +1,29 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+#
+# This file was generated by Bundler.
+#
+# The application 'standardrb' is installed as part of a gem, and
+# this file is here to facilitate running it.
+#
+
+require "pathname"
+ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../../Gemfile",
+  Pathname.new(__FILE__).realpath)
+
+bundle_binstub = File.expand_path("../bundle", __FILE__)
+
+if File.file?(bundle_binstub)
+  if File.read(bundle_binstub, 300) =~ /This file was generated by Bundler/
+    load(bundle_binstub)
+  else
+    abort("Your `bin/bundle` was not generated by Bundler, so this binstub cannot run.
+Replace `bin/bundle` by running `bundle binstubs bundler --force`, then run this command again.")
+  end
+end
+
+require "rubygems"
+require "bundler/setup"
+
+load Gem.bin_path("standard", "standardrb")