rpy2 is outdated


**Describe the current behavior**

rpy2 installed by default is an outdated version of rpy2 (3.4.5).

```python
import rpy2
rpy2.__version__
```

**Describe the expected behavior**

The code above returns 3.5.5.

**What web browser you are using**

Firefox.

**Additional context**

https://colab.research.google.com/drive/1pepfsZT8Zak_IxbH3XYxofUAogGkUn4c?usp=sharing
