Trying to fix travis build

.travis.yml

@@ -3,10 +3,14 @@ dist: xenial
 jdk:
   - openjdk8
 
-before_install: "mvn clean install -DskipTests=true -B -V -Pci-build"
+install: "mvn clean install -DskipTests=true -B -V -Pci-build"
 
 script: "mvn clean install -B -V -Pit-js -Pci-build"
 
+cache:
+    directories:
+    - $HOME/.m2
+
 branches:
     except:
         - gh-pages