Groups: Sync Stream, Accept Invite & Leave (#528)

* WIP support for reading groups from sync stream

Only does invites currently

* More support for parsing groups in the sync stream

* Fix jsdoc

src/client.js

@@ -659,6 +659,30 @@ MatrixClient.prototype.importRoomKeys = function(keys) {
     return this._crypto.importRoomKeys(keys);
 };
 
+// Group ops
+// =========
+// Operations on groups that come down the sync stream (ie. ones the
+// user is a member of or invited to)
+
+/**
+ * Get the group for the given group ID.
+ * This function will return a valid group for any group for which a Group event
+ * has been emitted.
+ * @param {string} groupId The group ID
+ * @return {Group} The Group or null if the group is not known or there is no data store.
+ */
+MatrixClient.prototype.getGroup = function(groupId) {
+    return this.store.getGroup(groupId);
+};
+
+/**
+ * Retrieve all known groups.
+ * @return {Groups[]} A list of groups, or an empty list if there is no data store.
+ */
+MatrixClient.prototype.getGroups = function() {
+    return this.store.getGroups();
+};
+
 // Room ops
 // ========
 
@@ -3423,6 +3447,17 @@ module.exports.CRYPTO_ENABLED = CRYPTO_ENABLED;
  * });
  */
 
+ /**
+ * Fires whenever the sdk learns about a new group. <strong>This event
+ * is experimental and may change.</strong>
+ * @event module:client~MatrixClient#"Group"
+ * @param {Group} group The newly created, fully populated group.
+ * @example
+ * matrixClient.on("Group", function(group){
+ *   var groupId = group.groupId;
+ * });
+ */
+
  /**
  * Fires whenever a new Room is added. This will fire when you are invited to a
  * room, as well as when you join a room. <strong>This event is experimental and