URLs are not correctly escaped for file names with spaces.

When direct access is turned on, this adapter does not escape file names when generating the URL. As a result, it is possible for the server to return invalid URLs for files with characters in the name, such as spaces, that should be escaped. As a result, some Parse clients, such as the iOS client, are unable to download files whose names have spaces in them.

To reproduce, create a file with a space in the name and attempt to access it via the iOS client.