Allow users to specify only a 'src' option and have it overwrite the file.

I actually submitted a pull-request to Grunt to allow this functionality out of the box - not accepted unfortunately. :(

Anyway, this PR will allow for users to only specify a SRC option and then it will overwrite each file that is matched.

```javascript
removelogging: {
      dist: {
        src: ["app/js/test/*.js"] /* all matching files will be overwritten */
      }
}
```