Deserialize array as Array object not ArrayList

[felipegs]

Days ago I have a problem with array objects with this filter.
When the json has an array, it deserialize the Array as Java ArrayList not as Ruby Array, I applied another filter on deserialized object that use map! method of Ruby Array and map! method does not work.

[jhitze]

This is causing issues in the logstash-output-riemann (logstash-plugins/logstash-output-riemann#9) as well.