Add nwm as target

This target installs the [nwm](https://github.com/mixu/nwm) window manager I wrote a while back. I'm using the [nodesource](https://github.com/nodesource/distributions) installer for the node dependency as recommended in [the Node project wiki](https://github.com/joyent/node/wiki/installing-node.js-via-package-manager), which supports i386 (32-bit), amd64 (64-bit) and armhf (ARM 32-bit hard-float, ARMv7 and up: arm-linux-gnueabihf) on a fairly wide range of distributions. Other than that dependency, everything is either native packages or node.js code.