[Work in progress] - Support for "JavaScript templates"

Many client side templating libraries recommend to deliver templates using ```script```. 

Example from http://handlebarsjs.com/
```
<script id="entry-template" type="text/x-handlebars-template">
  template content
</script>
```

Currently html-minifier does not support that.


This PR is not complete, as I am unsure if it is something this project would like to support, and if the way I am approaching the problem is the correct way.


Currently I need to fix an error with the parser.
This code
```
<script type="text/x-handlebars-template" id="id1" class="js_template">
    <h1 class="class1">title1</h1>    
</script>
```

is triggering this error
```"Unexpected token: operator (<)"```

PS: it is a work in progress! So I will compact the commit into one and add the documentation, clean style, etc
Need to be reverted before final review