Format under cursor causes loss of data.

Hi,

I'm running Text Tables version `0.1.5`.

Given:
```
| A| B|
| 1| 1|
| 0| 0|
|-1|-1|
```
Running format will render:
```
| A   | B   |
| 1   | 1   |
| 0   | 0   |
| --- | --- |
```
Thank you.