column formatting specifications not respected

[jldohmann]

Column width adjustments don't seem to work anymore. The following widths all render the same:

• [cols="a,a,a"] (should be auto width)

• [cols="1a,1a,2a"] (relative, third col is twice as wide as first two)

• [cols="25%a,25%a,50%a"] (same as previous, but explicitly with percentages)

• [cols="3*a"] (three equal width columns)

It results in a degraded user experience when the content becomes unreadable due to the inability to adjust columns. e.g.

The asciidoctor preview tool works as expected, but the asciibinder build does not.