Open first run page in background

lib/main.js

@@ -66,7 +66,8 @@ exports.main = function (options, callbacks) {
   }
   if (initialPage) {
     let initialPageUrl = data.url(initialPage);
-    tabs.open(initialPageUrl);
+    tabs.open({url: initialPageUrl,
+               inBackground: true});
     // Add a content script to open lightbeam if the corresponding button is
     // pressed in the inital page
     PageMod({