Only buttons show out
Hi, I just tried it and it only showed out buttons in my Sketch app. Is there something wrong with my html file? Thanks.

```
<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>JS Bin</title>
  <link href="https://fonts.googleapis.com/css?family=Roboto:400,500,700" rel="stylesheet">
  <link rel="stylesheet" href="style_guides.css">
</head>
<body>
  	<div data-sketch-symbol="Buttons/Primary"><button class='btn primary'>Button</button></div>
    <div data-sketch-symbol="Buttons/Secondary"><button class='btn secondary'>Button</button></div>
	<div data-sketch-text="Heading"><span class='hero-txt'><span>Hero text.</span></span></div>
    <div data-sketch-text="Heading" class='heading-txt'>Heading text</div>
    <div data-sketch-text="Heading" class='subheading-txt'>Subheading text</div>
    <h6>@jh-blue-pink</h6>
    <div data-sketch-color="#e60278" class='pink'></div>
	<h6>@jh-blue-lighter</h6>
    <div data-sketch-color="#2765cf" class='blue-lighter'></div>
</body>
</html>
```