fix splash screen height on iOS7

On iOS7, the status bar doesn't need to be offset from the splash screen height because of the new 'full screen' style of apps. The PR just adds a check for < v7.0 before subtracting the status bar height.

Tested in simulator for iOS 6.1 and 7.0 on both 3.5 and 4 inch models and fixes the issue.

EDIT: This PR refers to the issue being tracked at https://issues.apache.org/jira/browse/CB-4391