io.votable: Fix dropping of INFO element inside TABLE element

In VOTable 1.2, the INFO element is allowed before the DATA element inside of a TABLE element.  This fixes that.  

(For an example file, see http://gsss.stsci.edu/webservices/vo/ConeSearch.aspx?CAT=GSC23&RA=0&DEC=91.0&SR=0.1)

This was raised in an off-list e-mail discussion by @pllim.