IPAC table writer: request for help

This PR is an attempt to port `atpy`'s IPAC table writer to astropy.  Unfortunately, it looks like astropy's table format is missing a lot of the important metadata - most essentially, the column format - in the IPAC reader.  Can anyone familiar with the internals point out how I can get the appropriate metadata?  Do I simply need to re-write the reader?

Here's the test case I've been working with:
https://gist.github.com/keflavich/5050824