replaced fetch_task with get_task (#30)

Author: fatihkurtoglu

scaleapi/tasks.py

@@ -81,7 +81,7 @@ def as_dict(self):
 
     def refresh(self):
         """Refreshes the task details."""
-        self._json = self._client.fetch_task(self.id).as_dict()
+        self._json = self._client.get_task(self.id).as_dict()
 
     def cancel(self):
         """Cancels the task"""