Load configs and other text via getPackageDirectoryEntry()

Fixes #127
Turns out this isn't actually any faster, but it is cleaner and doesn't
clutter the console. We'll keep it for now.

js/util/text.js

@@ -1,6 +1,7 @@
 define(function() {
   
   var cache = {};
+  var directory = null;
   
   return {
     load: function(name, parentRequire, onLoad, config) {
@@ -8,12 +9,24 @@ define(function() {
         return onLoad(cache[name]);
       }
       
-      var xhr = new XMLHttpRequest();
-      xhr.open("GET", name);
-      xhr.onload = xhr.onerror = function() {
-        onLoad(xhr.responseText);
-      }
-      xhr.send();
+      var getFile = function() {
+        directory.getFile(name, {create: false}, function(entry) {
+          entry.file(function(file) {
+            var reader = new FileReader();
+            reader.onloadend = function() {
+              cache[name] = reader.result;
+              onLoad(reader.result);
+            };
+            reader.readAsText(file);
+          });
+        });
+      };
+
+      if (directory) return getFile();
+      chrome.runtime.getPackageDirectoryEntry(function(dir) {
+        directory = dir;
+        getFile();
+      });
     }
   };