JavascriptStringPipeline

Like the hogan pipeline, it would be great if cassette could set the template as a javascript string to a variable.

``` csharp
bundles.Add(
"HtmlTemplates"
// Assign the Hogan processor to the HTML template bundles
bundle => bundle.Processor = new JavascriptStringPipeline() {
JavaScriptVariableName = "JST"
}
);
```

This would allow me to use any templating engine I want.

It would render like

``` js
var JST = JST|| {};
JST['message'] = 'hello: <%= name %>';
```

Then I can reference in my code.

``` js
var compiled = _.template(JST['message']);
```