Zip file entries are incorrectly parsed as directories instead of class files

Obfuscated class files stored in the jar file which are suffixed with a directory separator character are incorrectly detected as directories. The JVM will still parse these pseudo-directories as class files.

See: https://github.com/sim0n/Caesium/blob/master/src/main/java/dev/sim0n/caesium/manager/ClassManager.java#L95