Fix config in readme: 'tcp' input is obsolete

This patch fixes the following warning I got when launching td-agent with the configuration supplied in README:

```
2013-12-09 19:51:56 +0900 [warn]: 'tcp' input is obsoleted and will be removed soon. Use 'forward' instead.
```

I also took the liberty of splitting the sample config into two parts: the source directive and the match directive. As far as I understand, the match directive isn't really a must to make this library work and therefore the README was a little misleading in saying "fluentd must be launched with the following config..."