Fix travis (#358)

Update travis.yml

Author: SUPERCILEX

.travis.yml

@@ -1,6 +1,15 @@
 language: android
-jdk:
-  - oraclejdk8
+jdk: oraclejdk8
+# See https://github.com/travis-ci/travis-ci/issues/5582
+sudo: required
+# See https://docs.travis-ci.com/user/languages/java/#Caching
+before_cache:
+  - rm -f  $HOME/.gradle/caches/modules-2/modules-2.lock
+  - rm -fr $HOME/.gradle/caches/*/plugin-resolution/
+cache:
+  directories:
+    - $HOME/.gradle/caches/
+    - $HOME/.gradle/wrapper/
 android:
   components:
     - platform-tools
@@ -13,5 +22,4 @@ android:
     - extra-google-m2repository
     - extra-android-m2repository
     - addon-google_apis-google-24
-script:
-  - ./gradlew clean :library:testAll :library:prepareArtifacts
+script: ./gradlew clean :library:testAll :library:prepareArtifacts