Lam Wei Li ac599e42c6
allow for zero backup - in sync with https://github.com/log4js-node/streamroller/pull/74
**Important**
It is also to note the file does not roll within itself (truncate its older entry for newer entry).
It truncates all and appends only the new entry.

```javascript
var rollers = require('streamroller');
var stream = new rollers.RollingFileStream('myfile', 6, 0);
stream.write("abc"); // add as first row
stream.write("def"); // add as second row
stream.write("ghi"); // truncate all and add as first row
stream.end();
```

Output:
```
myfile   - ghi
```
2022-01-20 01:47:15 +08:00
..