Support <small>.

Change-Id: I5dcf60362b26f49693d3e8c973032f50e8cbf294
Use an es6 Set to track templates.

Change-Id: I7ec659b3a5da6f44f5d2aad8729a3db60e7dd4e3
Document the need to export TEXINPUTS if building LaTeX sources manually.

Change-Id: Ic64128eb78fafbeb1c7e2bcf02e5583295fa2615
Add missing texlive-generic-extra dependency.

This is listed in the .travis.yml config (for Ubuntu 12) but it's also
needed for Ubuntu 13.  It provides `iftex.sty`.

Change-Id: I6a66a896d58b1b19d7a055ac331be71219dd68c7
Add childSelector/childSelectorAll helpers.

Also update to latest (unreleased) domino in order to get a working
implementation of Element.matches() and to fix the [lang] and [dir]
selectors.

Change-Id: I7a17c5d5ed5afdf4f035cee4fa43357d257a8801