Allow aliases to items with slashes in them

I ran into a problem where I needed to alias a file to a string with a "/" in it. Unfortunately, the current behavior is to assume that this means I want the alias destination resolved into a path.

I'm not sure why that behavior is useful, but proceeding on the assumption that it is, this patch checks to see if the expanded path actually exists before aliasing it. If it doesn't exist, it leaves the alias destination as is.