[CLEANUP] Drop EmogrifierTest::tearDown
[CLEANUP] Drop EmogrifierTest::tearDown

tearDown only contained unset($this->subject). As the unset is not
really necessary for helping the garbage collector, the complete
method can safely be removed.

Closes #131

jjriv/emogrifier,ricardofiorani/emogrifier,ernsto/emogrifier,iFixit/emogrifier,Seldaek/emogrifier,Synchro/emogrifier,MyIntervals/emogrifier,OzzyCzech/emogrifier,sanderkruger/emogrifier