Jackson 3.0.0 default for SerializationFeature.WRITE_DATES_AS_TIMESTAMPS

[cowtowncoder]

(part of #72 uber-Discussion)

As of Jackson 2.x, SerializationFeature.WRITE_DATES_AS_TIMESTAMPS defaults to true for backwards-compatibility. A suggestion has been made:

FasterXML/jackson-databind#4845

to change it to false instead, to improve JSON readability by defaulting to textual serialization over numeric timestamps which, while more efficient, are not human readable.
We cannot make the change in Jackson 2.x, but could change it for 3.0.0.

So let's see if there is consensus on whether to make proposed change.