(QENG-1225) Implement uber_build_with_polling.

Includes:
 * rspec tests for new jenkins utility methods
 * jenkins utility methods for grabbing information from given job url
 * `uber_build_with_polling` rake task that depends on `uber_build` then polls
   the resulting dynamic jenkins jobs and exits with nonzero exit status if any
   fail.

Signed-off-by: Wayne <wayne@puppetlabs.com>
(QENG-1225) Add optional polling behavior to `uber_build` task.

Signed-off-by: Wayne <wayne@puppetlabs.com>
(QENG-1225) Avoid "compilation nonsense".

Because no one likes nonsense.

Signed-off-by: Wayne <wayne@puppetlabs.com>
(QENG-1225) Use `fail` instead of `puts msg; exit 1`

Signed-off-by: Wayne <wayne@puppetlabs.com>
(QENG-1225) Fix documentation, remove poll value guard.

* Based on PR feedback, adding a polling interval value guard was deemed to be
  unnecessary and overreaching for the scope of this task.
* Removed some unnecessary jenkins puns.
* Minor README documentation clean up--create a sub heading to deal with polling
  behavior explanation.

Signed-off-by: Wayne <wayne@puppetlabs.com>
Merge pull request #341 from waynr/feature/master/QENG-1225

(QENG-1225) Implement uber_build polling and status query.