@Include.NON_DEFAULT doesn't work in newer versions of Jackson

[NodeAdam]

We are running a later Jackson version on our application server and this is causing this library to be unusable due to this bug.

In the case of Location.altitude (which is optional), not setting a value results in the field not being ignored as it appears in the pass.json file:

{ "latitude" : 37.33182, "longitude" : -122.03118, "altitude" : "NaN" }

This is not a valid format which results in the Wallet app not reading the pass.

I changed Include.NON_DEFAULT to Include.NON_NULL and set the default altitude value to null. This results in the same behavior as before the upgrade of Jackson.

I've created a pull request with a fix: https://github.com/ryantenney/passkit4j/pull/43