Enable setting of title for custom pages

* allowing custom title on page component

* Update about-slash.js

* Update help.js

* Update users.js

* Update versions.js

lib/server/server.js

@@ -442,6 +442,7 @@ function execute(port) {
         <Site
           language={language}
           config={siteConfig}
+          title={ReactComp.title}
           metadata={{id: path.basename(userFile, '.js')}}>
           <ReactComp language={language} />
         </Site>