Automatically upload Carthage.pkg upon tag push

Resolves #160.
Don't do anything for the Travis `install` step
Less verbose curling for WWDR certificate
Don't do anything for Travis `before_install` step
Disable Travis' automatic submodule behaviors

We already do this in script/cibuild, and Travis doesn’t automatically
initialize recursive submodules like we need.
Blow away most of cibuild, just use the Makefile
Join build signals using concat(), not then()

Resolves #147.
Add an error for no schemes being shared
Catch xcodebuild messages indicating no schemes
Bail out if xcodebuild -list hangs for ≥ 4 seconds

Works around #183.
Merge pull request #227 from Carthage/better-errors-without-schemes

Improve errors when no schemes are found
Merge pull request #226 from Carthage/fix-no-skip-current

Join build signals using concat(), not then()
Merge pull request #225 from Carthage/travis-auto-deploy

Automatically upload package via Travis when a tag is pushed
Allow build tool to be overridden.
Default to `xcodebuild`.
Build using `xctool` in Travis-CI.
Merge pull request #230 from jdhealy/travis-use-xctool

Build using `xctool` in Travis-CI.
Merge branch 'master' into 0.4-development

Conflicts:
	Carthage/Checkouts/Commandant
	Carthage/Checkouts/LlamaKit
	Carthage/Checkouts/Nimble
	Carthage/Checkouts/Quick
	Carthage/Checkouts/ReactiveCocoa
	Carthage/Checkouts/ReactiveTask
	Carthage/Checkouts/xcconfigs
	Source/CarthageKit/Errors.swift