Improving status overview

Hi all,

Thanks for the hard work, and quick developments on Nomad! @dadgar mentioned the improvements for the `status` command in #2969, which sounds really good!

I'm coming from deploying by hand (with Fabric), and thus always getting immediate feedback and status about jobs and deployments. Nomad is really fast, but also a bit obscure in what is going on. I am using Hashi-UI as well as the cli to get insight in what is going on, but that hasn't been too easy.

Therefore I have a suggestion for the output of status: that it is easier to infer the health of jobs. Currently:
```
⌘ nomad status
ID Type Priority Status Submit Date
app-production service 50 running 08/14/17 22:05:40 CEST
app-release service 50 running 08/15/17 09:34:04 CEST
django-script batch/parameterized 50 running 08/01/17 23:22:48 CEST
migrate batch/parameterized 50 running 08/13/17 20:55:52 CEST
migrate/dispatch-1502781729-48935f2d batch 50 dead 08/15/17 09:22:09 CEST
nginx system 50 running 08/09/17 23:21:20 CEST
```
shows me that all are running, but nothing more.

Then I run:
```
⌘ nomad status app-production
ID = app-production
Name = app-production
Submit Date = 08/14/17 22:05:40 CEST
Type = service
Priority = 50
Datacenters = NL1
Status = running
Periodic = false
Parameterized = false

Summary
Task Group Queued Starting Running Failed Complete Lost
api 0 0 2 0 12 0
celerybeat 0 0 1 0 6 0
default_worker 0 0 2 0 12 0
monitoring_worker 0 0 2 0 12 0
priority_worker 0 0 2 0 12 0
web 0 0 2 0 9 0

Latest Deployment
ID = 7e37943a
Status = failed
Description = Failed due to unhealthy allocations

Deployed
Task Group Auto Revert Desired Placed Healthy Unhealthy
api true 2 2 2 0
web true 2 1 0 1

Allocations
ID Node ID Task Group Version Desired Status Created At
35fd2089 bfbeae63 api 35 run running 08/14/17 22:06:07 CEST
1e807ba4 fd664622 monitoring_worker 35 run running 08/14/17 22:05:41 CEST
ad19d577 fd664622 default_worker 35 run running 08/14/17 22:05:41 CEST
24dc3c4b fd664622 api 35 run running 08/14/17 22:05:41 CEST
27f1601c fd664622 priority_worker 35 run running 08/14/17 22:05:41 CEST
2e4e79d5 fd664622 web 35 run running 08/14/17 22:05:41 CEST
1296b499 bfbeae63 priority_worker 35 run running 08/14/17 22:05:41 CEST
5c30510f fd664622 default_worker 35 run running 08/14/17 22:05:41 CEST
ae86f9e8 bfbeae63 celerybeat 35 run running 08/14/17 22:05:41 CEST
c1b3487c bfbeae63 monitoring_worker 35 run running 08/14/17 22:05:41 CEST
221fd4b3 bfbeae63 web 34 run running 08/13/17 18:20:20 CEST
```
which produces a lof of output, and also mentions "running" in the summary, and says everything is running fine in the "Summary" table. Only by looking at the "Latest deployment", or spotting different version numbers in the allocations table, is it that I learn that something isn't right.

I would like a bigger or more clear sign that something isn't right. Maybe `Status = running (unhealthy)` would be enough.

Related, I'm confused by the "Deployed" table: web has 2 desired, 1 placed, 0 healthy and 1 unhealthy. As you can see from the allocations, there are 2 web tasks running 34 & 35. Both are running (and thus "placed" somewhere), one is healthy (34) and one is unhealthy (35). So that line should imho be 2 2 1 1.

Start by tracing the Nomad CLI implementation for `nomad status`, then inspect how job health, deployment results, and allocation counts are assembled for the displayed tables. The work is done when status output clearly signals unhealthy jobs and the example deployment reports placed, healthy, and unhealthy allocations consistently.

Written by the indexing model from the issue text.