Fixed file list for multi-file torrents.

File.listFiles() will return files and 1st-level subdirectories. Any
subdirectories in files parameter of Torrent.create(4) will throw an error.
Also, the intention was probably to do a fully-recursive search.

FileUtils.listFiles() only returns files and is fully recursive.
Merge pull request #109 from cjmalloy/master

Fixed file list for multi-file torrents.