(cherry picked from commit 575f22e970e2429b8f9871f11b8c3e0924c82dc2)

IOPS have been modelled as a resource since Nomad 0.1 but has never
actually been detected and there is no plan in the short term to add
detection. This is because IOPS is a bit simplistic of a unit to define
the performance requirements from the underlying storage system. In its
current state it adds unnecessary confusion and can be removed without
impacting any users. This PR leaves IOPS defined at the jobspec parsing
level and in the api/ resources since these are the two public uses of
the field. These should be considered deprecated and only exist to allow
users to stop using them during the Nomad 0.9.x release. In the future,
there should be no expectation that the field will exist.

Should provide cut and paste example for most users. Advanced users should be able to correct URLs to something appropriate.

Switch from global-redis-check for the example job's service name to
redis-cache. The former name is really confusing and someone finally
called us out on it:

https://groups.google.com/d/msg/nomad-tool/3RTh6CyYkWk/vEe_Sj7lAAAJ

Also specifically mention that the `service.name` parameter is what is
advertised in Consul.

This PR updates the api documentation to reflect 0.6 HTTP API and the
JSON job specification as well.

Caught some typos.  Made units separate from the numbers 1GHz -> 1 GHz
after talking to Nick about questions of style (this has the side effect of making future spell checking easier).