Fix assets compilation for some cases

This fixes two problems I've had with assets compilation and adds comments to methods:
- removes references **sourceMaps** from compiled files, so there are no failed requests to these when using DevTools
- Adds a newline between merged files. Seems that some libraries don't end with one and I had a problem when using jQuery + Bootstrap:
```
...code
// comment file A
```
and
```
/*!
 * comment file B
 */
code...
```
was merged into:
```
...code
// comment file A/*!
* comment file B
*/
code...
```