Also install new porter dep

This commit reworks the Vagrantfile for Nomad in order to support
straightforward testing on more than one operating system, whilst
retaining the ability to stand up a test cluster running Ubuntu.

The following changes are made:

- Scripts have been extracted from the Vagrantfile into their own shell
  script files, in order that editors lint them.

- All scripts have been edited to lint with no warnings or errors for
  their respective shells.

- Scripts are named according to the operating system and privilege
  level which they run. We prefer to run a whole shell script as root
  versus prefixing (essentially) every command with `sudo` or an
  equivalent.

- The Linux development box has been separated from the test cluster,
  removing some of the more gnarly (and less portable) logic. The Linux
  development box is still primary and autostarts.

- A FreeBSD target has been added. The base box works for both
  Virtualbox and VMWare Fusion.

- A target is added to the GNUmakefile to stand up a test cluster, using
  the default provider, or overriding the provider by setting the PROVIDER
  variable in make:
	- `make testcluster`
	- `make testcluster PROVIDER=vmware_fusion`

- Machines in the test cluster have Avahi configured for zeroconf
  discovery. Each machine can ping each other machine at `hostname.local`
  - for example `nomad-server02.local`, `nomad-client03.local`.

This commit replaces the shell script-driven build process for Nomad
with one based around GNU Make (note we _do_ use GNU-specific
constructs), requiring no additional scripts for common cases of
development. The following targets are implemented:

Per-OS/arch combinations:

    Binaries (Host - Mac OS X):
	pkg/darwin_amd64/nomad

    Binaries (Host - Linux):
	pkg/linux_386/nomad
	pkg/linux_amd64/nomad
	pkg/linux_amd64-lxc/nomad
	pkg/linux_arm/nomad
	pkg/linux_arm64/nomad
	pkg/windows_386/nomad
	pkg/windows_amd64/nomad

    Packages (Host - Mac OS X):
	pkg/darwin_amd64.zip

    Packages (Host - Linux):
	pkg/linux_386.zip
	pkg/linux_amd64.zip
	pkg/linux_amd64-lxc.zip
	pkg/linux_arm.zip
	pkg/linux_arm64.zip
	pkg/windows_386.zip
	pkg/windows_amd64.zip

Phony targets:

	dev - Builds for the current host GOOS/GOARCH (unless overriden
	      in the environment)

	release - Builds all appropriate release packages for the
	          current host GOOS/GOARCH (i.e. Wind...

This reverts commit 9f2ea928.

gox has not been used since commit 1aec23bb, so there is no need to
install it during bootstrap.

Vault is required for the fingerprinting tests but is not currently
installed by the build process. This commit adds a new category of
external tools for test dependencies and `go get`'s them during the
bootstrap.

We also fix the syntax of the Makefile to use tabs throughout.

make dev properly copies the binary into bin/ again.

make release still creates binaries for as many archs as possible.

Fixes #2407

This PR fixes our vet script and fixes all the missed vet changes.

It also fixes pointers being printed in `nomad stop <job>` and `nomad
node-status <node>`.

Saves a backup file using a gitignored extension.

The dev build is far simpler than the release build, so move it to its
own shell script. This simplifies the release build script slightly as
well at the cost of duplicating the version/tag logic.

Also don't even try to check for LXC if not running on Linux. I don't
think we want to try to support cross-compiling LXC from non-Linux
hosts.