Tabular numbers should be used on tables
**Describe the bug**
Tables rendered in Jupyter Lab (likely also Jupyter Notebook), e.g. from pandas, do not use tabular numbers. This causes sorted columns to look unsorted and makes numbers harder to read and compare.

**To Reproduce**

Create a table like this:

<img width="299" alt="Screenshot 2019-06-14 at 08 38 42" src="https://user-images.githubusercontent.com/204911/59488447-dc541700-8e7f-11e9-8aff-50274888859c.png">

**Expected behavior**

With tabular numbers applied through CSS:

<img width="302" alt="Screenshot 2019-06-14 at 08 41 07" src="https://user-images.githubusercontent.com/204911/59488557-3228bf00-8e80-11e9-917d-62e6024233bf.png">

CSS used to apply tabular numbers:

```
table { font-variant-numeric: tabular-nums; }
```

**Screenshots**

Screenshots attached above.

**Desktop (please complete the following information):**

- OS: Any
- Browser: Any
- JupyterLab: Tested on 0.35.6, but probably applies to any version of Jupyter Lab

