Add Carthage/Commandant to workspace
Replace Command.swift with Commandant
Completely remove now-empty CarthageTests
Remove annoying search path added by Xcode
Merge pull request #129 from Carthage/extract-commandant

Extract Command and ArgumentParser into Commandant.framework
Add purposely broken static library to RCL fixture
Add a method to obtain product types
Skip non-framework targets
Expose ProductType, create type for build settings
Refactor Xcode functions to use BuildSettings type
Remove unnecessary `let`
Use filter(identity) on booleans
Merge branch 'only-build-frameworks' into fix-multi-target-schemes
Refactor BuildSettings to load once per target
Refactor shouldBuildScheme() for multiple targets
Update platformForScheme() for multiple targets
Refactor buildScheme() to support multiple targets
Build RCL unit tests with Mac framework target

This helps test that build settings are aggregated across all targets, not just one of them (randomly).
Add empty framework built with RCL iOS scheme

Used to test that all framework targets in a scheme are built.
Log exact task invocations to stdout and stderr

Resolves #91.