Added /shortcuts (#3048)

Added message and tests

Remember that lower vs uppercase matters

Accidentally removed \n

Added more

Formatted

api/command_shortcuts_test.go

@@ -0,0 +1,21 @@
+// Copyright (c) 2016 Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package api
+
+import (
+	"github.com/mattermost/platform/model"
+	"strings"
+	"testing"
+)
+
+func TestShortcutsCommand(t *testing.T) {
+	th := Setup().InitBasic()
+	Client := th.BasicClient
+	channel := th.BasicChannel
+
+	rs := Client.Must(Client.Command(channel.Id, "/shortcuts ", false)).Data.(*model.CommandResponse)
+	if !strings.Contains(rs.Text, "ALT") {
+		t.Fatal("failed to display shortcuts")
+	}
+}