Update Dockerfile and README to Hadoop 3.3.4 (#26)

diff --git a/Dockerfile b/Dockerfile
index 6aa631e..d22b05c 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -41,7 +41,7 @@
 ##
 FROM buildbase as hadoop
 
-ARG HADOOP_VERSION=3.3.3 \
+ARG HADOOP_VERSION=3.3.4 \
   HADOOP_FILE=_NOT_SET
 
 # Copy a known file along with the optional files (that might not exist).
diff --git a/README.md b/README.md
index 6c709fe..256907e 100644
--- a/README.md
+++ b/README.md
@@ -17,7 +17,7 @@
 | Software    | Version       |
 |-------------|---------------|
 | [Accumulo]  | 2.1.0         |
-| [Hadoop]    | 3.3.3         |
+| [Hadoop]    | 3.3.4         |
 | [ZooKeeper] | 3.8.0         |
 
 If these versions do not match what is running on your cluster, you should consider building