Added meta tag for responsiveness.

plugin/emmet.vim

@@ -23,6 +23,7 @@
 "      | <head>
 "      |     <title></title>
 "      |     <meta charset="UTF-8">
+"      |     <meta name="viewport" content="width=device-width, initial-scale=1.0">
 "      | </head>
 "      | <body>
 "      |      _