* Markdown reader: simple tables are now given column widths of 0.
* Column width of 0 is interpreted as meaning: use default column width.
* Writers now include explicit column width information only
for multiline tables. (Exception: RTF writer, which requires
column widths. In this case, columns are given equal widths,
adding up to the text width.)
* Simple tables should now look better in most output formats.
git-svn-id: https://pandoc.googlecode.com/svn/trunk@1631 788f1e2b-df1e-0410-8736-df70ead52e1b
