add quest image to party page for collection quests - fixes https://github.com/HabitRPG/habitrpg/issues/3892

without this fix:
![screen shot 2014-08-21 at 6 29 22 am](https://cloud.githubusercontent.com/assets/1495809/3987711/b81dac58-28a8-11e4-8903-b3c9425d0667.png)

with this fix:
![screen shot 2014-08-21 at 6 29 50 am](https://cloud.githubusercontent.com/assets/1495809/3987721/c3fd82fa-28a8-11e4-8a11-264b028f8b8d.png)