Layers structure with initramfs, rootfs and usersfs
Adapted docker images to exec /init automatically

Don't work with initramfs because it's not generated from a Dockerfile, though
Remove NPM and Node-GYP caches
Shell at boot as parameter
Improved security

Build-generated files only accesible by its owner
System umask set to 0077
removed unneded unsecure kernel mounts (/proc & /sys)
rootfs re-mount as read-only (needs fixing)
filesystems mounts with NODEV & NODUID flags
In Docker, don't bring a shell by default
barebones layer booting directly to Node.js REPL
Using logon instead of hard-coded shell
Use '/sbin/init' by default, don't need to specify it
Use compiled Linux kernel with bundled Node.js executable
Barebones initramfs build from file instead of explicit folder
Simplified permissions on initramfs
Don't need to use sudo

There's an issue with genext2fs on usersfs that makes logon to give an EACCESS error, needs some more investigation since it doesn't give more info.
Don't need sudo to generate images and improved filesystem security
Self-build Node.js shared libraries & update kernel to 3.18.0-rc4
Use OverlayFS
Updated documentation
Merge pull request #64 from NodeOS/AUFS

Use layers based on OverlayFS