feat(docs): link to unit repo in example deployment
feature(agent,machine): track job resource requirements and machine specs

On the agent level, remember what each job declares for resource requirements.
This will be queried from systemd in the future.
This PR does not yet publish the free space on the machine to etcd yet.
codereview feedback
more codereview work
Merge pull request #459 from robszumski/link-unit-repo

feat(docs): link to unit repo in example deployment
fix(systemd): fix logic bug: break vs. return

Break only exits from the innermost for/select/switch.
Includes a couple minor style tweaks nearby also.
Merge pull request #481 from burke/fixbreak

Fix logic bug where break didn't exit as many levels as intended.
Merge pull request #441 from uwedeportivo/machineload

feature(agent,machine): track job resource requirements
style(*): ran gofmt -s and made golint changes

* omitting type annotations for literals when inferrable from context
* (`gofmt -s`)
* omitting second `range` key when ignored (`k, _` -> `k`, `gofmt -s`)
* Idiomatic error messages: Start lowecase, except where referencing an
* uppercase value/type, no terminal punctuation (`golint`)
* `errors.New(fmt.Sprintf(args))` -> `fmt.Errorf(args)` (`golint`)
* `if foo { return bar } else { baz }` -> `if foo { return bar } baz`
* (`golint`)

Conflicts:
	fleetctl/ssh_test.go
Merge pull request #482 from burke/gofmt-s-golint

gofmt -s and golint
feat(unit): add InstanceUnit helpers
feat(job): substitute Requirements for instance unit jobs