spec: basic once-ler integration, speed up some specs

see https://github.com/instructure/once-ler

in rails3, reduce spec/models/a* runtime by ~45% (15min -> 8.5min locally)

Change-Id: Ia7bbc36c3602c3c3742c1b894e539584323f3e14
Reviewed-on: https://gerrit.instructure.com/37043
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Dave Donahue <ddonahue@instructure.com>
Product-Review: Jon Jensen <jon@instructure.com>
QA-Review: Jon Jensen <jon@instructure.com>