Added support for type `requirejs`

Added support for type `requirejs`
This will add optional 4th param to generated script tag as an attribute.
This could be a generic solution for those looking for adding attributes to generated `<script>` tag 

Example: 
```js
<!-- build:requirejs scripts/bootstrap.js data-main="scripts/bootstrap"  -->
<script data-main="scripts/config" src="../bower_components/requirejs/require.js"> </script>
<!-- endbuild -->
```
will be replaced with 
```js
<script data-main="scripts/bootstrap" src="scripts/bootstrap.js"></script>
```