Trying to build using JDK 7

Author: DanielaSfregola

.travis.yml

@@ -19,13 +19,22 @@ after_success:
 
 scala:
   - 2.12.3
-  - 2.12.1
-  - 2.11.8
+  - 2.11.11
   - 2.10.6
 
 jdk:
+  - oraclejdk7
   - oraclejdk8
 
+matrix:
+  exclude:
+  - scala: 2.12.3
+    jdk: oraclejdk7
+  - scala: 2.10.6
+    jdk: oraclejdk8
+  - scala: 2.11.11
+    jdk: oraclejdk8
+
 env:
   - SBT_OPTS="-XX:+UseConcMarkSweepGC -XX:+CMSClassUnloadingEnabled -XX:PermSize=256M -XX:MaxPermSize=512M"