Re-enable testing against older iOS SDKs in CI
Re-enable testing against older iOS SDKs in CI

The more SDKs we work against the merrier! Looks like Travis has re-added
support for testing against the 5.0 and 5.1 iOS SDKs since we had to originally
take them out in this commit:

    8aef6e7ccfbce87b6cf170260ce08e1faf3d7f83

jasperblues/cedar,jasperblues/cedar,pivotal/cedar,idoru/cedar,pivotal/cedar,briancroom/cedar,jasperblues/cedar,jeffh/cedar,jeffh/cedar,briancroom/cedar,idoru/cedar,pivotal/cedar,idoru/cedar,irfanah/cedar,jeffh/cedar,briancroom/cedar,hsienchiaolee/cedar,tjarratt/cedar,jeffh/cedar,tjarratt/cedar,pivotal/cedar,tjarratt/cedar,hsienchiaolee/cedar,tjarratt/cedar,pivotal/cedar,hsienchiaolee/cedar,briancroom/cedar,irfanah/cedar,idoru/cedar,irfanah/cedar,jasperblues/cedar,irfanah/cedar,briancroom/cedar,hsienchiaolee/cedar,idoru/cedar,jeffh/cedar,tjarratt/cedar