Fix JDK download URL (final fix)

travis.sh

@@ -15,8 +15,8 @@ installJdk8() {
   pushd ~/jvm > /dev/null
   if [ ! -d "jdk1.8.0_181" ]; then
     wget --quiet --continue --header "Cookie: oraclelicense=accept-securebackup-cookie" http://download.oracle.com/otn-pub/java/jdk/8u181-b13/96a7b8442fe848ef90c96a2fad6ed6d1/jdk-8u181-linux-x64.tar.gz
-    tar xzf jdk-8u171-linux-x64.tar.gz
-    rm jdk-8u171-linux-x64.tar.gz
+    tar xzf jdk-8u181-linux-x64.tar.gz
+    rm jdk-8u181-linux-x64.tar.gz
   fi
   popd > /dev/null
   export JAVA_HOME=~/jvm/jdk1.8.0_171