Updated POM to use the latest version of Thumbnailator.

There were reports of OutOfMemoryErrors occuring when using Thumbnailator with the latest versions of Java 6 and 7. (Java 6 Update 45 and Java 7 Update 21)

Thumbnailator 0.4.4 addresses the OutOfMemoryError issue by fixing a bug that was preventing resources from being released after reading and writing images.

This should address the "OutOfMemoryError: Java heap space" problems encountered by some PS3 Media Server users. One such instance can be found in the following forum posting:
http://www.ps3mediaserver.org/forum/viewtopic.php?f=6&t=16692

For more information, please refer to the Issue Tracker of Thumbnailator:
http://code.google.com/p/thumbnailator/issues/detail?id=42