Support installation via Carthage for macOS and tvOS

[1ec5]

According to the CocoaPods podspec, this project supports macOS 10.9+ and tvOS 9.0+ alongside iOS. However, the Xcode project only has a scheme for iOS, which means this library can’t be installed for a macOS or tvOS project using Carthage. The fix would be to add two additional framework targets, two additional schemes, and the required entries in the Travis configuration file.