upgrade jackson for test app (#246)

Author: thomaszurkan-optimizely

test-app/build.gradle

@@ -48,7 +48,7 @@ dependencies {
     // https://mvnrepository.com/artifact/org.slf4j/slf4j-android
     compile group: 'org.slf4j', name: 'slf4j-android', version: '1.7.25'
     // EXAMPLE REPLACE gson json parsing with jackson-databind json parsing.
-    compile group: 'com.fasterxml.jackson.core', name: 'jackson-databind', version: '2.9.6'
+    compile group: 'com.fasterxml.jackson.core', name: 'jackson-databind', version: '2.9.8'
 
     testCompile "junit:junit:$junit_ver"
     testCompile "org.mockito:mockito-core:$mockito_ver"