Show 5 most recent "Private messages" when clicked.

Like the Stream Subject lists, Private messages are now shown
when the user clicks on the "Private message" link. User can drill in
to get more than 5 conversations. Selecting PMs from the user or group
PM lists on the right sidebar also opens the list & highlights the
selected conversation.

[Edited by tabbott@mit.edu to fix some small bugs.]

frontend_tests/node_tests/stream_list.js

@@ -13,6 +13,9 @@ add_dependencies({
 
 set_global('recent_subjects', new global.Dict());
 set_global('unread', {});
+set_global('message_store', {
+    recent_private_messages: new global.Array()
+});
 
 var stream_list = require('js/stream_list.js');
 
@@ -23,6 +26,7 @@ $.fn.expectOne = function () {
 };
 
 global.use_template('sidebar_subject_list');
+global.use_template('sidebar_private_message_list');
 global.use_template('stream_sidebar_row');
 global.use_template('stream_privacy');
 
@@ -46,6 +50,29 @@ global.use_template('stream_privacy');
     assert.equal(topic, 'coding');
 }());
 
+(function test_build_private_messages_list() {
+    var reply_tos = "alice@zulip.com,bob@zulip.com";
+    var active_conversation = "Alice, Bob";
+    var max_conversations = 5;
+
+
+    var conversations = {reply_to: reply_tos,
+                      display_reply_to: active_conversation,
+                      timestamp: 0 };
+    global.message_store.recent_private_messages.push(conversations);
+
+    global.unread.num_unread_for_person = function () {
+        return 1;
+    };
+
+    var convos_html = stream_list._build_private_messages_list(active_conversation, max_conversations);
+    global.write_test_output("test_build_private_messages_list", convos_html);
+
+    var conversation = $(convos_html).find('a').text().trim();
+    assert.equal(conversation, active_conversation);
+}());
+
+
 (function test_add_stream_to_sidebar() {
     // Make a couple calls to add_stream_to_sidebar() and make sure they
     // generate the right markup as well as play nice with get_stream_li().