Add https://raw.github.com/tianon/gentoo-overlay/master/repositories.xml to overlays section in /etc/layman/layman.cfg (as per instructions on the Gentoo Wiki), then invoke the following:
layman -f -a tianon
After performing those steps, the following should work (or any other package from this overlay):
sudo emerge -av app-emulation/tilem
The app-emulation/lxc-docker (and companion app-emulation/lxc-docker-bin) package has moved to its own repository. For your convenience, that repository has been added to the repositories.xml file here so that you can simply invoke the following to keep up:
layman -f -a docker
layman -d tianon # optional, but you no longer need my personal overlay
If you'd like to modify your layman.cfg to point to the docker-overlay repositories.xml file directly instead of mine, use something similar to the following:
sed -i 's!/tianon/gentoo-overlay/!/tianon/docker-overlay/!' /etc/layman/layman.cfg