fix arguments format

"doneFunction" is an argument in `grunt.util.spawn` function, and according to the situation above(I extracted them bolew), "`doneFunction`" may be better than "done function".

> ### grunt.util.repeat
> Return string `str` repeated `n` times.

> ### grunt.util.pluralize
> Given `str` of `"a/b"`, If `n` is `1`, return `"a"` otherwise `"b"`. You can specify a custom separator if '/' doesn't work for you.