This PR adds tracking to when a task starts and finishes and the logs
API takes advantage of this and returns better errors when asking for
logs that do not exist.

This PR adds the following metrics to the client:
client.allocations.migrating
client.allocations.blocked
client.allocations.pending
client.allocations.running
client.allocations.terminal

Also adds some missing fields to the API version of the evaluation.

api.AgentSelf mirrors command.agent.agentSelf, and makes it easier to
work with the results of a call to Agent.Self()

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>`.

This PR removes defaulting from the parse, fixes some regressions that
existed as part of the parser refactor and fixes the tests.

The format of the missing port error message changed from Go 1.7 to 1.8.
The fix is to just use strings.Contains instead of strings.HasPrefix
when looking for the "missing port" part.

Also add an error return to Client.newRequest as parsing the path
processes arbitrary user input and would panic if given an invalid URL.

See: https://groups.google.com/d/topic/nomad-tool/gi3-CTE7oXo/discussion