Move presentations submodule to website

.gitmodules

@@ -1,3 +1,3 @@
 [submodule "doc/presentations"]
-	path = doc/presentations
+	path = website/presentations
 	url = https://github.com/yandex/clickhouse-presentations.git

website/gulpfile.js

@@ -36,7 +36,7 @@ var paths = {
         '!node_modules/**/*.{jpg,jpeg,png,svg,ico}',
         '!public/**/*.{jpg,jpeg,png,svg,ico}'],
     robotstxt: ['robots.txt'],
-    presentations: ['../doc/presentations/**/*']
+    presentations: ['presentations/**/*']
 };
 
 gulp.task('clean', function () {