Switched to Travis Trusty image

See: https://docs.travis-ci.com/user/trusty-ci-environment/

Author: Majid Mallis

.travis.yml

@@ -1,4 +1,5 @@
-sudo: false
+sudo: required
+dist: trusty
 install: true
 
 branches:
@@ -16,7 +17,7 @@ notifications:
 
 jdk:
   - oraclejdk8
-  - oraclejdk7
+  - openjdk7
 
 script: mvn -X clean test