Add /docs.json route redirecting to the most recent doc manifest on the CDN

cc @trollixx

lib/app.rb

@@ -17,7 +17,7 @@ class App < Sinatra::Application
     set :assets_prefix, 'assets'
     set :assets_path, -> { File.join(public_folder, assets_prefix) }
     set :assets_manifest_path, -> { File.join(assets_path, 'manifest.json') }
-    set :assets_compile, %w(*.png docs.js application.js application.css application-dark.css)
+    set :assets_compile, %w(*.png docs.js docs.json application.js application.css application-dark.css)
 
     require 'yajl/json_gem'
     set :docs_prefix, 'docs'
@@ -64,7 +64,7 @@ class App < Sinatra::Application
     use Rack::Deflater
     use Rack::Static,
       root: 'public',
-      urls: %w(/assets /docs /images /favicon.ico /robots.txt /opensearch.xml /manifest.webapp),
+      urls: %w(/assets /docs/ /images /favicon.ico /robots.txt /opensearch.xml /manifest.webapp),
       header_rules: [
         [:all,           {'Cache-Control' => 'no-cache, max-age=0'}],
         ['/assets',      {'Cache-Control' => 'public, max-age=604800'}],
@@ -171,6 +171,10 @@ class App < Sinatra::Application
     200
   end
 
+  get '/docs.json' do
+    redirect asset_path('docs.json')
+  end
+
   get '/s/maxcdn' do
     redirect 'https://www.maxcdn.com/?utm_source=devdocs&utm_medium=banner&utm_campaign=devdocs'
   end

test/app_test.rb

@@ -173,6 +173,14 @@ class AppTest < MiniTest::Spec
     end
   end
 
+  describe "/docs.json" do
+    it "returns to the asset path" do
+      get '/docs.json'
+      assert last_response.redirect?
+      assert_equal 'http://example.org/assets/docs.json', last_response['Location']
+    end
+  end
+
   describe "/feed" do
     it "returns an atom feed" do
       get '/feed'