allow array syntax inside of the messageKey property of a config item

index.js

@@ -265,9 +265,8 @@ Clay.prepareForAppMessage = function(val) {
 
   if (Array.isArray(val)) {
     result = [];
-    val.forEach(function(item) {
-      var itemConverted = Clay.prepareForAppMessage(item);
-      result.push(itemConverted);
+    val.forEach(function(item, index) {
+      result[index] = Clay.prepareForAppMessage(item);
     });
   } else if (typeof val === 'object' && val) {
     if (typeof val.value === 'number') {
@@ -297,20 +296,54 @@ Clay.prepareForAppMessage = function(val) {
  * assign arrays into individual keys
  * @see {prepareForAppMessage}
  * @param {Object} settings
- * @param {Object} messageKeys
  * @returns {{}}
  */
-Clay.prepareSettingsForAppMessage = function(settings, messageKeys) {
-  var result = {};
+Clay.prepareSettingsForAppMessage = function(settings) {
+
+  // flatten settings
+  var flatSettings = {};
   Object.keys(settings).forEach(function(key) {
+    var val = settings[key];
+    var matches = key.match(/(.+?)(?:\[(\d*)\])?$/);
+
+    if (!matches[2]) {
+      flatSettings[key] = val;
+      return;
+    }
+
+    var position = parseInt(matches[2] || 0, 10);
+    key = matches[1];
+
+    if (typeof flatSettings[key] === 'undefined') {
+      flatSettings[key] = [];
+    }
+
+    flatSettings[key][position] = val;
+  });
+
+  var result = {};
+  Object.keys(flatSettings).forEach(function(key) {
     var messageKey = messageKeys[key];
-    var settingArr = Clay.prepareForAppMessage(settings[key]);
+    var settingArr = Clay.prepareForAppMessage(flatSettings[key]);
     settingArr = Array.isArray(settingArr) ? settingArr : [settingArr];
 
     settingArr.forEach(function(setting, index) {
-      result[messageKey + index] = setting;
+      if (typeof setting !== 'undefined') {
+        result[messageKey + index] = setting;
+      }
     });
   });
+
+  // validate the settings
+  Object.keys(result).forEach(function(key) {
+    if (Array.isArray(result[key])) {
+      throw new Error('Clay does not support 2 dimensional arrays for item ' +
+                      'values. Make sure you are not attempting to use array ' +
+                      'syntax (eg: "myMessageKey[2]") in the messageKey for ' +
+                      'components that return an array, such as a checkboxgroup');
+    }
+  });
+
   return result;
 };