Proposal get rid of `repoze.xmliter` using equivalent `lxml` tools

[ale-rt]

it's beyond the scope of this fix, but I was doing a transform yesterday and changed getHTMLSerializer from repoze.xmliter with lxml.etree.HTMLParser. Should we actually move to that one?
repoze.itertools does not look much taken care of 😓
And actually it is just a tiny wrapper to lxml...

Originally posted by @gforcada in #239 (comment)