Update example to new iOS sdk and new xcode-plugin

The iOS 7.0 sdk is not part of the default install of recent Xcode versions.
Update iOS sdk version to 7.1, and update to the latest release of the gradle xcode plugin.
Add missing Xcode scheme

The build.gradle references an Xcode scheme that is not marked as shared.
Thus, the Gradle build fails unless you first open the project in Xcode and have it autocreate the scheme.

This change makes it possible to build the project from Gradle without first opening it in Xcode.
Merge pull request #61 from perchrh/master

Minor updates to build Example with Xcode 5.1