deps should respect skip-recommended

For example, `brew deps libass --skip-recommended` shouldn't print
harfbuzz because, even though libass builds with harfbuzz when harfbuzz
is not skipped, we asked to skip recommended, of which harfbuzz is one.

The corresponding change is made for `brew uses` as well.

Thanks to Xu Cheng for contributing the code. Any errors are mine.

Closes #129.

Signed-off-by: ilovezfs <ilovezfs@icloud.com>