Merge remote-tracking branch 'origin/master' into alamofire5

# Conflicts:
#	.travis.yml
#	Alamofire.podspec
#	Alamofire.xcodeproj/project.pbxproj
#	Alamofire.xcodeproj/xcshareddata/xcschemes/Alamofire iOS.xcscheme
#	Alamofire.xcodeproj/xcshareddata/xcschemes/Alamofire macOS.xcscheme
#	Alamofire.xcodeproj/xcshareddata/xcschemes/Alamofire tvOS.xcscheme
#	Source/Request.swift
#	Source/ServerTrustPolicy.swift
#	Source/SessionManager.swift
#	Source/TaskDelegate.swift
#	Tests/DownloadTests.swift
#	Tests/MultipartFormDataTests.swift
#	Tests/ResultTests.swift