Update exim-spam

attached sample Exim log line to demonstrate a silently tossed message as described at https://github.com/fail2ban/fail2ban/issues/533
ENH: exim-spam to include spamassassin log entry. Closes gh-533
ENH: end anchor for exim-spam
Update exim-spam

An example with no valid FROM email address and host without reverse DNS record
MRG: test cases on exim-spam
DOC: for exim-spam to say how to enable the log lines for the latest regex
DOC: fix ChangeLog entry for exim-spam
Merge pull request #536 from grooverdan/exim-spam

ENH: exim-spam - also block based on emails "discarded" by spamassassin