pb.write and print don't work in jupyter notebook

The version used is 350640d3171a568fb3f22d64d898e154541acc56
Neither
```python
with tqdm(...) as pb:
    pb.write("test")
```
nor

```
with tqdm(...) as pb:
     print("test")
```

work.
It turned out that the text output is buffered somehow, and flushed only if there are lot of lines. It is not flushed even on cell execution finish.

