Do not shade jackson.  Instead, include it as a dependency.

Shading jackson was causing the jackson serializers to ignore annotations
on objects (since the classes of those objects used the 'real' jackson annotations
(under com.fasterxml.jackson.annotation),
but the shaded jackson classes were expecting the shaded classes
(under net.logstash.logback.encoder.com.fasterxml.jackson.annotation).
Merge branch 'master' into remove-shaded-jackson
Merge pull request #48 from philsttr/remove-shaded-jackson

Remove shaded jackson