enforce a better email wrapping to send valid emails

Refs https://github.com/cakephp/cakephp/commit/ff0aa70b59befdf11d17b8e5646e24ab6c4e9aec#commitcomment-3271576

Only one test is not yet passing - wrapping too long links in testWrapLongLine() (CakeEmailTest.php : 1883)