support for single quotes

Hi, 

in HTML you can specify tag attributes using either single quotes or double quotes as in example bellow:

```html
<!-- build:js /data/js/app.js -->
<script src='js/lib.js'></script>
<script src='js/main.js'></script>
<!-- endbuild -->
```
I have changed the regular expressions to allow any of the styles.

Regards,
Adrian