Carthage support

[miguelangel-dev]

In order to integrate the most important dependency managers in nef, we will add support to Carthage.

• Break CocoaPods dependency to install nef and build template. (tracked in Remove CocoaPods dependency from playground install #88)
• nef compiler add Carthage supports to compiler | clean | dependencies options. (tracked in Carthage compiler #90)
• nef playground should be compatible with third-party libraries using Carthage - add --carthage flag (tracked in Carthage playground support #91)
• Update README to include this new flag in nef playground + information about Carthage supports