Updating the method to remove the reply thread for mails sent using Zimbra Emal client.

We now look for <hr id="zwchr"> and if we don't find that <hr> we proceed with the blockquote as we used to.
Merge pull request #15 from tipitnet/fix-6514

Fix 6514
Merge pull request #16 from tipitnet/test

Fix for 6514