fix filemode in tests (#28)

This fixes #20 by using a more restrictive filemode during tests.

linux_test.go

@@ -15,7 +15,7 @@ func TestMaintainMode(t *testing.T) {
 
 	filename := logFile(dir)
 
-	mode := os.FileMode(0770)
+	mode := os.FileMode(0600)
 	f, err := os.OpenFile(filename, os.O_CREATE|os.O_RDWR, mode)
 	isNil(err, t)
 	f.Close()