cache Gradle artifacts for travis (except the lock file) (closes #266)
cache Gradle artifacts for travis (except the lock file) (closes #266)

paulk-asert/incubator-groovy,jwagenleitner/groovy,russel/groovy,paplorinc/incubator-groovy,apache/groovy,apache/incubator-groovy,shils/groovy,paulk-asert/incubator-groovy,apache/incubator-groovy,armsargis/groovy,russel/incubator-groovy,shils/groovy,graemerocher/incubator-groovy,paulk-asert/incubator-groovy,dpolivaev/groovy,apache/incubator-groovy,apache/groovy,shils/incubator-groovy,alien11689/incubator-groovy,shils/groovy,avafanasiev/groovy,paplorinc/incubator-groovy,dpolivaev/groovy,jwagenleitner/incubator-groovy,russel/incubator-groovy,paulk-asert/incubator-groovy,shils/incubator-groovy,bsideup/incubator-groovy,shils/incubator-groovy,paulk-asert/groovy,russel/groovy,paulk-asert/groovy,armsargis/groovy,traneHead/groovy-core,russel/groovy,tkruse/incubator-groovy,paplorinc/incubator-groovy,apache/groovy,armsargis/groovy,dpolivaev/groovy,shils/incubator-groovy,alien11689/incubator-groovy,apache/groovy,russel/incubator-groovy,pledbrook/incubator-groovy,tkruse/incubator-groovy,jwagenleitner/groovy,paulk-asert/incubator-groovy,graemerocher/incubator-groovy,armsargis/groovy,traneHead/groovy-core,pledbrook/incubator-groovy,bsideup/incubator-groovy,tkruse/incubator-groovy,bsideup/incubator-groovy,tkruse/incubator-groovy,avafanasiev/groovy,alien11689/incubator-groovy,dpolivaev/groovy,russel/groovy,fpavageau/groovy,jwagenleitner/incubator-groovy,alien11689/incubator-groovy,graemerocher/incubator-groovy,russel/incubator-groovy,bsideup/incubator-groovy,fpavageau/groovy,traneHead/groovy-core,avafanasiev/groovy,paplorinc/incubator-groovy,jwagenleitner/incubator-groovy,jwagenleitner/incubator-groovy,jwagenleitner/groovy,graemerocher/incubator-groovy,fpavageau/groovy,paulk-asert/groovy,apache/incubator-groovy,pledbrook/incubator-groovy,pledbrook/incubator-groovy,fpavageau/groovy,shils/groovy,traneHead/groovy-core,jwagenleitner/groovy,paulk-asert/groovy,avafanasiev/groovy