via @kylef

via @segiddins

via @segiddins

* origin/sandbox_reorganization_544:
  [Integration] Update
  [Integration] Update fixtures
  [Specs] Minor fix
  Rebuilding fixtures again.
  fixing .xcconfig tests and output.
  Fixed integration tests to work with sandbox.
  Regenerated integration files.
  Last unit test updates for sandbox.
  File references and target installer tests updated for new sandbox layout.
  Fixing more tests to look for files in the correct spots.
  Many test fixes.
  External sources and sandbox analyser spec tests fixed to work with new migrator.
  [WIP] Integrating migrator with tests.
  Initial work for sandbox reorganization

Conflicts:
	examples/AFNetworking iOS Example/AFNetworking iOS Example.xcworkspace/contents.xcworkspacedata
	lib/cocoapods/external_sources.rb
	lib/cocoapods/installer.rb
	lib/cocoapods/installer/target_installer.rb
	lib/cocoapods/sandbox.rb
	lib/cocoapods/sandbox/headers_store.rb
	spec/cocoapods-integration-specs
	spec/unit/external_sources_spec.rb
	spec/unit/generator/xcconfig/aggregate_xcconfig_spec.rb
	spec/unit/hooks/library_representation_spec.rb
	spec/unit/installer/analyzer/sandbox_analyzer_spec.rb
	spec/unit/installer/file_references_installer_spec.rb
	spec/unit/installer/pod_source_installer_spec.rb
	spec/unit/installer/target_installer/aggregate_target_installer_spec.rb
	spec/unit/installer/target_installer/pod_target_installer_spec.rb
	spec/unit/installer/user_project_integrator/target_integrator_spec.rb
	spec/unit/installer/user_project_integrator_spec.rb
	spec/unit/installer_spec.rb
	spec/unit/library_spec.rb
	spec/unit/project_spec.rb
	spec/unit/sandbox/headers_store_spec.rb
	spec/unit/sandbox_spec.rb
	spec/unit/target/aggregate_target_spec.rb
	spec/unit/target/pod_target_spec.rb

Closes #2320

hg (and git, for that matter) is required to run the install_subspecs spec. As a result, this
commit makes the Rake tasks die quickly if it is not installed.

Closes https://github.com/CocoaPods/CocoaPods/issues/2388

* lookback-pods-by-config: (45 commits)
  [UserProjectIntegrator] Warn about xcconfig override after every installation /2
  [UserProjectIntegrator] Warn about xcconfig override after every installation
  [AggregateTarget] Add #user_targets
  [AggregateTarget] Documentation cleanup
  [Bundle] Update
  [PodTarget] Ensure that subspecs are on the same configurations
  add a space to the override warning
  [Docs] Some small fixes.
  [Changelog]
  [Integration] Disable xcproj in Xcodeproj
  [Project] Coherce preprocessor definitions to an array
  [PrivatePodXcconfig] Add inherited to GCC_PREPROCESSOR_DEFINITIONS
  [Project] Add preprocessor definition for build configurations
  [TargetEnvironmentHeader] Refactor
  [AggretateTarget] Expose specs by build configuration
  [PrefixHeader] Style fixes
  [Xcodeproj]: Fix issue for libraries with a space in the name
  [Examples] Update integration
  [Installer] Use downcase to validate configurations
  [XCConfigIntegrator] Downcase the name of the build configurations
  ...

Conflicts:
	CHANGELOG.md
	Gemfile.lock
	lib/cocoapods/installer.rb
	lib/cocoapods/target/aggregate_target.rb
	spec/integration.rb