Update to 1.4.0
* Implement Feature #2952: Mail_mime::headers() saves extra headers [cipri]
* Implement Feature #3636: Allow specification of charsets and encoding [cipri]
* Implement Feature #4057: Mail_Mime: Add name parameter for Content-Type [cipri]
* Implement Feature #4504: addHTMLImage does not work in cases when filename contains a path [cipri]
* Implement Feature #5837: Mail_Mime: Build message for Net_SMTP [cipri]
* Implement Feature #5934: Mail_Mime: choice for content disposition [cipri]
* Implement Feature #6568: Mail_Mime: inline images referenced in CSS definitions not replaced. [cipri]
* Implement Feature #10604: Put an option to specify Content-Location in the header [cipri]

(adrianp)