use 'rebar ct' for 'make travis' so return code for run is right in R15

Makefile

@@ -35,7 +35,6 @@ binary: clean all
 	(cd ../rebar.wiki && git commit -m "Update $(VSN)" rebar)
 
 test:
-	mkdir -p test/logs
-	ct_run -pa deps/*/ebin -pa ebin -include include -logdir test/logs -dir test
+	rebar ct
 
 travis: all test