CHANGED: do not throw on error

[warpdesign]

del makes use of the globby package which takes a list of globs as parameter and returns a promise with the list of valid patterns.

So, with this directory tree:

/foo
/foo/bar
/access_denied

The code globby(['/bar', '/foo']) would return ['/foo']`.

So calling del(['/bar', '/foo']) would simply delete /foo and return `['/foo'] without any error.

While calling del(['access_denied', '/foo']) would reject the promise with a permission error, but /foo would have been deleted and there's no way to know it.

This pull_request attempts to make error handling more consistent, so both previous calls would return ['/foo'] so the developer can find if there was an error by comparing the original array and the returned array's length.