Feature/upgrade jackson and bson4jackson

See: https://github.com/devbliss/mongojack/issues/48 

Upgrading dependencies for Jackson to 2.3.2 and Bson4Jackson to 2.3.1. Changes are covered by existing tests and all tests have passed. 

The main motivation behind this upgrade is to prevent potential conflicts with Jackson 2.2.X when using frameworks which require Jackson 2.3.X, such as Dropwizard. Thanks!