Update installation directions for Carthage
Update installation directions for Carthage

LayerKit doesn't get built since it's already a binary, it remains in the Checkouts folder

classic-chris/Atlas-iOS,charlespsdowd/Atlas-iOS,daninfpj/Atlas-iOS,bright/Atlas-iOS,misberri/Atlas-iOS,geoffmacd/Atlas-iOS,jaderfeijo/Atlas-iOS,hellosimplify/Atlas-iOS,jeff-riffsy/Atlas-iOS,mailyan/Atlas-iOS,bandlab/Atlas-iOS