I3-gaps

Building on ubuntu or pi

sudo apt-get install xcb libx11-xcb-dev libxcb-keysyms1-dev libsdl-pango-dev libxcb1-dev libxcb-keysyms1-dev libpango1.0-dev libxcb-util0-dev libxcb-icccm4-dev libyajl-dev libstartup-notification0-dev libxcb-randr0-dev libev-dev libxcb-cursor-dev libxcb-xinerama0-dev libxcb-xkb-dev libxkbcommon-dev libxkbcommon-x11-dev

cd development
git clone https://www.github.com/Airblader/i3 i3-gaps
cd i3-gaps
# do this if you want the stable branch, skip it if you want the dev branch (gaps-next)
git checkout gaps && git pull
make
sudo make install

Then reboot and continue to use i3 as window manager.