updated to iphone ios 7.1

No errors reported at all against a full Sauce suite of unit and functional tests (only running the ios 7.1 environment)
e.g. https://saucelabs.com/tests/305e4d582baa48dc8c981ab8999f67e8

No guarantee it'll stay that way but seems to run better than 7.0

(I pushed from master as it's just a config change)