Resolve "Use cache in CI for gradle"

Closes #27 (closed)

.gitlab-ci.yml

@@ -2,6 +2,14 @@ stages:
 - build
 - test
 
+before_script:
+  - export GRADLE_USER_HOME=`pwd`/.gradle
+
+cache:
+  paths:
+    - .gradle/wrapper
+    - .gradle/caches
+
 build:
   image: openjdk:8
   stage: build