Explain how schemes are found in subprojects vs. workspaces

This feels like a tricky one. Currently, Quick already builds Nimble. But if you want to manage Nimble separately (which you probably do), there's no way to specify that you should use the version of Nimble.framework from the Nimble repository. Carthage builds Nimble first (I'm assuming because of alphabetical sorting?) then builds Quick, which clobbers the version built by Nimble.

Not sure if this should be opened with Quick as well (their installation instructions say to install them separately). But an "easy" (if heavy-handed) way to resolve this might be to install dependencies in the order that they are listed in the Cartfile.

/cc @modocache