Adjusted WARC-Date for Revisit-Records

[awaldlza]

trafficstars

Fix for Issue 31 (hopefully):

Changed method: make_index_revisit

Information about the WARC-Date of the index record is passed on to the create_revisit_record-method, so that the revisit record gets the same WARC-Date entry as the index record. Accordingly, the revisit record also gets a WARC-Creation-Date with the actual timestamp of the creation of the record.

As far as tested it works both with --fixed-dt and with the original time stamp of files that are "warced".