TableModeRealign strips leading whitespace in cell

I have a table cell that has a ReST code block, which has leading whitespace. When I call `TableModeRealign`, the leading spaces are stripped, which collapses the structure of the code in the block.

For example:

```
+-------------+-----------------------------------------------------------------------+
| filters | JSON object representing a simplified query, of this form:: |
| | |
| | { |
| | "field1": ["value1", "value2"], |
| | "field2": ["value3"] |
| | } |
```

becomes

```
+-------------+-----------------------------------------------------------------------+
| filters | JSON object representing a simplified query, of this form:: |
| | |
| | { |
| | "field1": ["value1", "value2"], |
| | "field2": ["value3"] |
| | } |
```

So far this is my _only_ issue with this extremely useful plugin. Thanks!