Add Support tvOS, watchOS, macOS

[wmcginty]

Investigate and implement support for tvOS, watchOS and macOS. This would involve creating new framework targets for each of these operating systems as well as new example projects.

Note that may involve switching the build system of this workspace over to Carthage. See Hyperspace for an example.

[tylermilner]

Whoever picks this up, feel free to explore utilizing the existing Cocoapods pod lib create project structure to get everything working. Although, I kind of like Hyperspace's structure a little better, I can think of 2 problems with it currently:

• Potential for a discrepancy between the dependencies defined in the Podspec and the dependencies defined in the Cartfile. These probably won't change much, but you still have to remember to update them in both spots.
• Complexity introduced with SwiftLint utilization. Requiring contributors to have SwiftLint installed locally isn't ideal since they will also need to keep that installation up-to-date or else CI checks could fail.

On the other hand, the Cocoapods library template format doesn't seem to be very widely adopted by the community so maybe we should follow community conventions.

For everything to work on Travis, I think we just need to concentrate on getting the 3 test targets (UtiliKit-iOSTests, UtiliKit-tvOSTests, and UtiliKit-macOSTests) for the 4 example targets building - (UtiliKit-iOSExample, UtiliKit-tvOSExample, UtiliKit-watchOSExample, and UtiliKit-macOSExample. Since each one should bring in its respective version of UtiliKit, that should be good enough to prove that the library builds for that platform (in addition to the test target running).