Conflicts:
	spec/unit/command_spec.rb

Addresses https://github.com/CocoaPods/CocoaPods/commit/0c80af37f1fec0009ad63277309afa47ad22595f#commitcomment-7718723.

Closes #2156.

Grammar

Thanks @segiddins

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.