Add shared schemes for installation by Carthage.

[yoichitgy]

Added shared schemes to install ExSwift by Carthage:
https://github.com/Carthage/Carthage

[pNre]

I'm new to Carthage, allow me a couple of days to check everything is ok before merging.
Anyway, thanks for your contribution.

[yoichitgy]

Thank you. My motivation to use Carthage instead of CococaPods is to reduce time to build a project. Carthage builds added frameworks only once when carthage update runs. In contrast, CocoaPods builds added frameworks every time when a workspace is built unless 'Find Implicit Dependencies' is unchecked in the build scheme.

As mentioned in the Carthage project, CocoaPods has amazing features, but I think Carthage is also nice to manage dynamic frameworks. (For a framework developer, Carthage needs no extra effort after creating the shared schemes.)