TINKERPOP-1884 Bump to TinkerPop 4.0.56.Final

CHANGELOG.asciidoc

@@ -34,6 +34,7 @@ image::https://raw.githubusercontent.com/apache/tinkerpop/master/docs/static/ima
 * Removed hardcoded expectation in metrics serialization test suite as different providers may have different outputs.
 * Added `IndexedTraverserSet` which indexes on the value of a `Traverser` thus improving performance when used.
 * Utilized `IndexedTraverserSet` in `TraversalVertexProgram` to avoid extra iteration when doing `Vertex` lookups.
+* Bumped to Netty 4.0.56.Final.
 * Fixed a bug in Gremlin Console which prevented handling of `gremlin.sh` flags that had an "=" between the flag and its arguments.
 * Fixed bug where `SparkMessenger` was not applying the `edgeFunction` from `MessageScope`.
 * Fixed a bug in `ComputerAwareStep` that didn't handle `reset()` properly and thus occasionally produced some extra traversers.

pom.xml

@@ -147,7 +147,7 @@ limitations under the License.
         <javadoc-plugin.version>2.10.4</javadoc-plugin.version>
         <jcabi.version>1.1</jcabi.version>
         <metrics.version>3.0.2</metrics.version>
-        <netty.version>4.0.53.Final</netty.version>
+        <netty.version>4.0.56.Final</netty.version>
         <slf4j.version>1.7.21</slf4j.version>
         <snakeyaml.version>1.15</snakeyaml.version>
         <spark.version>1.6.1</spark.version>