upgrade jackson to 2.8.6

Closes #751, #467.

Author: mattnworb

pom.xml

@@ -89,17 +89,17 @@
     <dependency>
       <groupId>com.fasterxml.jackson.jaxrs</groupId>
       <artifactId>jackson-jaxrs-json-provider</artifactId>
-      <version>2.6.0</version>
+      <version>2.8.6</version>
     </dependency>
     <dependency>
       <groupId>com.fasterxml.jackson.datatype</groupId>
       <artifactId>jackson-datatype-guava</artifactId>
-      <version>2.6.0</version>
+      <version>2.8.6</version>
     </dependency>
     <dependency>
       <groupId>com.fasterxml.jackson.core</groupId>
       <artifactId>jackson-databind</artifactId>
-      <version>2.6.0</version>
+      <version>2.8.6</version>
     </dependency>
     <dependency>
       <groupId>org.glassfish.jersey.core</groupId>