Suport for href attribute
in order for the <a> tag (part of #5 (closed)) to be useful, support for the href HTML attribute will be necessary. Syntax for it should be something like this:
(a (href "http://dailyprog.org/") "link to dailyprog.org!")
It would be best if this were made into a macro function, so that the code can be reused for other string-like HTML attributes. However, if it isn't that way initially, that's fine.