Reorder YAML representers to favor customs

By default, snakeyaml will only represent a ConfigurationSerializable if
it does not extend a class already provided with a Representer (Number, 
List, Map, Set, Iterator, Object[], Date, Enum and Calendar.)

Reordering the representers to place the custom classes first allows
a plugin author to explicitly override the default object serialization
and deserialization and still extend the default representer classes.

http://code.google.com/p/snakeyaml/source/browse/src/main/java/org/yaml/
snakeyaml/representer/SafeRepresenter.java?name=v1.9#49