Fix 'Extract Binaries to Disk' docs.

Author: ruebot

docs/extract-binary.md

@@ -14,10 +14,10 @@ files, spreadsheet files, and presentation program files to disk?
 
 ```scala
 import io.archivesunleashed._
-import io.archivesunleashed.udfs._
+import io.archivesunleashed.df._
 
 // Web archive collection.
-warcs = RecordLoader.loadArchives("/path/to/warcs", sc)
+val warcs = RecordLoader.loadArchives("/path/to/warcs", sc)
 
 // Audio Files.
 warcs.audio()