fix(tests): don't make assumptions about the user's system
fix(client): restore `--cluster=dev` as apps:create default

In refactoring the Deis CLI docstrings, we broke the default cluster
for apps:create. This was pointed out by smoke_test.go.
fix(tests): use aufs in builder functional tests

We had previously switched to Ubuntu's default for Docker,
devicemapper. But aufs has proven to be faster and more reliable
for the CI system itself, and when we switched CI nodes to aufs we
did not do so with the builder functional test itself.
Merge pull request #1443 from deis/aufs-in-builder-tests

fix(tests): use aufs in builder functional tests
Merge pull request #1441 from deis/1440-fix-cli-default-cluster

fix(client): restore `--cluster=dev` as apps:create default
Merge pull request #1439 from deis/fix/tests/Xe

fix(tests): don't make assumptions about the user's system
fix(userdata template): put motd directly in the OS

Same kind of fix as PR 1444. Trivial fix that saves a systemd unit from
being run needlessly.
Merge pull request #1445 from deis/fix/userdata/motd

fix(userdata template): put motd directly in the OS
fix(userdata template): put `nse` function in FHS

Gentoo's `/etc/profile` automatically sources all `.sh` files in
`/etc/profile.d` when bash is run. This reduces boot time at the expense
of an extra file read per shell opened. However this is a minimal cost
for the FHS convenience. Trivial fix.