Added "Extension" string translate

youtube_dl_gui/locale/ru_RU/LC_MESSAGES/youtube_dl_gui.po

@@ -5,7 +5,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: youtube-dlg 0.3.8\n"
 "POT-Creation-Date: 2015-07-02 15:31+EEST\n"
-"PO-Revision-Date: 2015-11-22 10:05+0300\n"
+"PO-Revision-Date: 2015-11-22 10:38+0300\n"
 "Last-Translator: Nikita «Arttse» Bystrov <arttsesoft@gmail.com>\n"
 "Language-Team: ru\n"
 "Language: ru\n"
@@ -102,6 +102,10 @@ msgstr "Выключение системы"
 msgid "Title"
 msgstr "Заголовок"
 
+#: mainframe.py:108
+msgid "Extension"
+msgstr "Расширение"
+
 #: mainframe.py:110
 msgid "Size"
 msgstr "Размер"