Add getSyncToken and setSyncToken to data store interface.

This allows local storage to hold onto the token across page refreshes.

lib/store/localstorage.js

@@ -17,6 +17,22 @@ function LocalStorageStore() {
 
 LocalStorageStore.prototype = {
 
+    /**
+     * Retrieve the token to stream from.
+     * @return {string} The token or null.
+     */
+    getSyncToken: function() {
+        return null;
+    },
+
+    /**
+     * Set the token to stream from.
+     * @param {string} token The token to stream from.
+     */
+    setSyncToken: function(token) {
+
+    },
+
     /**
      * Store a room in local storage.
      * @param {Room} room

lib/store/memory.js

@@ -16,10 +16,27 @@ module.exports.MatrixInMemoryStore = function MatrixInMemoryStore() {
     this.users = {
         // userId: User
     };
+    this.syncToken = null;
 };
 
 module.exports.MatrixInMemoryStore.prototype = {
 
+    /**
+     * Retrieve the token to stream from.
+     * @return {string} The token or null.
+     */
+    getSyncToken: function() {
+        return this.syncToken;
+    },
+
+    /**
+     * Set the token to stream from.
+     * @param {string} token The token to stream from.
+     */
+    setSyncToken: function(token) {
+        this.syncToken = token;
+    },
+
     /**
      * Store the given room.
      * @param {Room} room The room to be stored. All properties must be stored.

lib/store/stub.js

@@ -5,15 +5,31 @@
  */
 
 /**
- * Construct a stub store. This does no-ops on all store methods.
+ * Construct a stub store. This does no-ops on most store methods.
  * @constructor
  */
 function StubStore() {
-
+    this.fromToken = null;
 }
 
 StubStore.prototype = {
 
+    /**
+     * Get the sync token.
+     * @return {string}
+     */
+    getSyncToken: function() {
+        return this.fromToken;
+    },
+
+    /**
+     * Set the sync token.
+     * @param {string} token
+     */
+    setSyncToken: function(token) {
+        this.fromToken = token;
+    },
+
     /**
      * No-op.
      * @param {Room} room