FYI: rootfs refactoring

[Frank Hunleth]

If you update nerves-sdk, you'll get several changes that I've been
making to the root filesystem. Most of them involve code cleanup and
making sure that Buildroot generated images are built the same way as
images built out of your Erlang/Elixir project directories. I did
change the rootfs sizing parameters, so if you run into any issues,
please let me know. The result is that rootfs images are 2 MB smaller
for small projects and, for me, on a larger project I saved about 40
MB (almost 50%). If you're wondering why I waited until now to do
this, the reason is that before I had unionfs support everywhere, I
had to leave some slack in the image to let it be mounted read-write.
The slack calculation wasn't the greatest as is probably obvious from
the stats.

Frank

--
Frank Hunleth
Troodon Software LLC
Embedded Software Development
http://troodon-software.com/