Improved handling of directories inside a zip file

Zip/Zip.swift

@@ -215,6 +215,9 @@ public class Zip {
             guard let filePath = path.path else {
                 throw ZipError.ZipFail
             }
+            var isDirectory: ObjCBool = false
+            fileManager.fileExistsAtPath(filePath, isDirectory: &isDirectory)
+            if !isDirectory {
                 let input = fopen(filePath, "r")
                 if input == nil {
                     throw ZipError.ZipFail
@@ -262,6 +265,7 @@ public class Zip {
                 free(buffer)
                 fclose(input)
             }
+        }
         zipClose(zip, nil)
         
         // Completed. Update progress handler.