Refine `sep` rule according to @sharwell's suggestion(danielsun1106/groovy-parser#27)
Refine `sep` rule according to @sharwell's suggestion(danielsun1106/groovy-parser#27)

apache/incubator-groovy,shils/incubator-groovy,paulk-asert/groovy,paulk-asert/groovy,shils/incubator-groovy,paulk-asert/incubator-groovy,apache/incubator-groovy,russel/incubator-groovy,shils/groovy,apache/incubator-groovy,traneHead/groovy-core,apache/groovy,jwagenleitner/incubator-groovy,russel/incubator-groovy,shils/groovy,armsargis/groovy,apache/groovy,paulk-asert/incubator-groovy,russel/groovy,jwagenleitner/groovy,apache/groovy,traneHead/groovy-core,jwagenleitner/incubator-groovy,jwagenleitner/incubator-groovy,traneHead/groovy-core,apache/groovy,jwagenleitner/groovy,russel/incubator-groovy,russel/groovy,shils/groovy,jwagenleitner/groovy,russel/groovy,traneHead/groovy-core,paulk-asert/incubator-groovy,paulk-asert/incubator-groovy,shils/groovy,armsargis/groovy,apache/incubator-groovy,shils/incubator-groovy,russel/groovy,armsargis/groovy,paulk-asert/incubator-groovy,russel/incubator-groovy,armsargis/groovy,paulk-asert/groovy,paulk-asert/groovy,jwagenleitner/incubator-groovy,shils/incubator-groovy,jwagenleitner/groovy