v2.0.0-alpha.4

• Changed ContentNegotiator to MediaParserNegotiator
• Removed ContentNegotiator::addContentType
• Removed ContentNegotiator:: getMediaParserForContentType
• Removed ContentNegotiator:: getPreferredContentTypeFromRequest
• Changed ContentNegotiator:: getPreferredMediaParserFromRequest to MediaParserNegotiator::fromRequest
• Changed ContentNegotiator:: addMediaParser to MediaParserNegotiator::add
• Removed HttpFactoryInterface
• Changed Tests directory structure
• Moved xml extension dependencies to suggestions
• Removed AbstractRouter::addControllerActionFromPath() + related tests