Added text to cover the new support in Universe for Xenial.
### Ubuntu
+nvme-cli is supported in the Universe package sources for Xenial for
+many architectures. For a complete list try running:
+ ```
+ rmadison nvme-cli
+ nvme-cli | 0.3-1 | xenial/universe | source, amd64, arm64, armhf, i386, powerpc, ppc64el, s390x
+ ```
A Debian based package for nvme-cli is currently maintained as a
Ubuntu PPA. Right now there is support for Trusty, Vivid and Wiley. To
install nvme-cli using this approach please perform the following