Fix object propertu dereferencing

src/RescueTime/Activity.php

@@ -132,7 +132,7 @@ public function __construct($rowHeaders, $columns)
 
         foreach ($columns as $key => $value) {
             if (array_key_exists($key, $properties)) {
-                $this->$poperties[$key] = $value;
+                $this->$key = $value;
             }
         }
     }