Update Hadoop to 2.8.4 (#183)

diff --git a/conf/checksums b/conf/checksums
index 56918cf..b6c925e 100644
--- a/conf/checksums
+++ b/conf/checksums
@@ -5,6 +5,7 @@
 accumulo:1.7.3:294f2f1f3fbc164b68e80cecd5a6ce5c245df804fb35ae5e03ab1c86bc9480da
 hadoop:3.0.2:0d507aa71007b2685e292343c11c2cb90a92ea7625446b57d1fb47c5721e2f82
 hadoop:2.9.0:8d48666f29f9ade6ed2762b7a9edab177bad2c57396f43d0ffd6a269d54f6fe1
+hadoop:2.8.4:63007792ecaf566aa8b97779db22805461ff3542fd18f14a60b3bcca1c6831bdeb6c9bb6d59596914fc6cc92c2049ce183e29c41aa10a97f5193fd3284a47acb
 hadoop:2.8.3:e8bf9a53337b1dca3b152b0a5b5e277dc734e76520543e525c301a050bb27eae
 hadoop:2.7.6:f2327ea93f4bc5a5d7150dee8e0ede196d3a77ff8526a7dd05a48a09aae25669
 hadoop:2.7.5:0bfc4d9b04be919be2fdf36f67fa3b4526cdbd406c512a7a1f5f1b715661f831
diff --git a/conf/uno.conf b/conf/uno.conf
index eff6cee..746f02d 100644
--- a/conf/uno.conf
+++ b/conf/uno.conf
@@ -3,7 +3,7 @@
 
 # Versions
 # --------
-export HADOOP_VERSION=${HADOOP_VERSION:-2.7.6}
+export HADOOP_VERSION=${HADOOP_VERSION:-2.8.4}
 export ZOOKEEPER_VERSION=${ZOOKEEPER_VERSION:-3.4.12}
 export ACCUMULO_VERSION=${ACCUMULO_VERSION:-1.9.1}
 export SPARK_VERSION=${SPARK_VERSION:-1.6.3}