Calling Yajl.load with ARGF hangs after last object

Calling `Yajl.load(ARGF)` will hang after the last object has been yielded.

E.g.
```bash
echo '{"a": 1}' | ruby -ryajl -e 'Yajl.load(ARGF) {|o| p o }'
```
Will output
```
{"a"=>1}
``` 
and then hang indefinitely.
