Allow to set assets host with ASSETS_HOST

This can be used to set a specific host for a CDN.

config.ru

@@ -63,5 +63,5 @@ run Travis::Web::App.build(
   customer_io_site_id: ENV['CUSTOMER_IO_SITE_ID'],
   pro: ENV['TRAVIS_PRO'],
   code_climate: ENV['CODE_CLIMATE'],
-  code_climate_url: ENV['CODE_CLIMATE_URL']
+  code_climate_url: ENV['CODE_CLIMATE_URL'],
 )

lib/travis/web/app.rb

@@ -94,6 +94,7 @@ class Travis::Web::App
       else
         set_config(content, options) if config_needed?(file)
         set_title(content) if index?(file)
+        set_assets_host(content) if index?(file)
 
         headers = {
           'Content-Length'   => content.bytesize.to_s,
@@ -158,6 +159,10 @@ class Travis::Web::App
       content.gsub!(/\{\{title\}\}/, ENV['SITE_TITLE'] || default_title)
     end
 
+    def set_assets_host(content)
+      content.gsub!(/\{\{assets_host\}\}/, ENV['ASSETS_HOST'] || '')
+    end
+
     def set_config(string, opts = {})
       string.gsub! %r(<meta (rel|name)="travis\.([^"]*)" (href|value)="([^"]*)"[^>]*>) do
         %(<meta #{$1}="travis.#{$2}" #{$3}="#{options[$2.to_sym] || $4}">)

public/index.html

@@ -23,8 +23,8 @@
     <link rel="dns-prefetch" href="//api.github.com">
     <link rel="dns-prefetch" href="//www.gravatar.com">
     <link rel="icon" type="image/png" href="/favicon.ico">
-    <link rel="stylesheet" href="/styles/app.css">
-    <script src="/scripts/app.js"></script>
+    <link rel="stylesheet" href="{{assets_host}}/styles/app.css">
+    <script src="{{assets_host}}/scripts/app.js"></script>
     <script>
       minispade.require('travis')
       Travis.run()