Allow mutliple files

Hey,

even though we use the 'files' object formet to supply the source it wasn't actually processing multiple files within one target. 

I wrote an update, added tests and made few changes to have it actually support multiple files like such:

```javascript
targethtml: {
    dist: {
        files: {
            "dist/index.html": "app/index.html",
            "dist/mobile.html": "app/mobile.html"
        }
    }
}
```