SwiftNIO support & dynamicMemberLookup

• Add support for SwiftNIO EventLoopFuture based API
• Separate out TravisV3Core package for Codable types.
• Use keypath dynamicMemberLookup on Metadata & Embed
• Add small example CLI using ArgumentParser
• Currently depends on a fork of async-http-client until an escaping issue is resolved - PR here
• Rename Meta -> Metadata