Add setTo method to SimpleEmailServiceMessage (#56)

Add setTo method as a shorthand of clearTo->addTo

Author: bravadomizzou

src/SimpleEmailServiceMessage.php

@@ -63,6 +63,17 @@ public function addTo($to) {
 
  return $this;
  }
+ 
+ /**
+ * @return SimpleEmailServiceMessage $this
+ */
+ public function setTo($to) {
+ $this->to = (array) $to;
+ 
+ $this->is_clean = false;
+ 
+ return $this;
+ }
 
  /**
  * Clear the To: email address(es) for the message