The concept of keywords with a name, value, and possibly comment/description and unit is generic and occurs in many contexts.  So I think it should be handled by the general `Table` class.  I have thought about this in fits and starts (pun intended), but never come to a good solution.  The obvious thing is just a simple container class Keyword that has those attributes, but then you need to do `t.meta['key'].value`.  Maybe `Quantity` can work for keywords as well (with some enhancement)?  Just thinking out loud I'm not sure.

And I don't know if I'm influenced by FITS, but I always think of keywords as being a *list* of things which might not be unique by name.  In this case access by name `t.meta[name]` is something dynamic that responds differently depending on how many keyword names matched `name`.