Striped columns

## Expected Behavior

I'd like to be able to stripe the columns on a very dense table. I can find examples for striped rows, like this one: https://github.com/gregnb/mui-datatables/issues/201 but not for columns.

## Current Behavior

I tried to adapt the example in https://github.com/gregnb/mui-datatables/issues/201 by doing:

MUIDataTableBodyCell: {
cellStacked: {
"&:nth-child(odd)" : {
background: "gray"
},
}

but this makes everything gray.

## Your Environment

| Tech | Version |
|--------------|---------|
| Material-UI | 4.4.0 |
| MUI-datatables | 2.10.2 |
| React | 16.9.0 |
| browser | Chrome |
| etc | |

Start by reproducing the reported styling attempt with MUI-datatables 2.10.2, React 16.9.0, and Material-UI 4.4.0, then compare it with the striped-row example in issue #201. Done means a dense table can alternate column backgrounds without making every cell gray.

Written by the indexing model from the issue text.