AsyncHTTPClient 1.6.0

This release completely replaces the internal HTTP1Connection and HTTPConnectionPool. The new implementations are more performant and enable new features down the road like: async/await and HTTP/2.

SemVer Minor

• New HTTP1Connection (#386, #388, #396, #400, #423, #425, #430, #431, #432, #435, #441, #442)
• New HTTPConnectionPool (#384, #397, #398, #402, #404, #412, #413, #415, #416, #417, #419, #420, #421, #422, #427, #428, #433, #434, #438)
• Make connection pool size configurable (#437)

SemVer Patch

• Refactor Request Validation (#391)
• [ConnectionFactory] Replace (Channel, HTTPVersion) with NegotiatedProtocol (#399)
• New HTTP2Connection - not enabled for now (#401)
• Use explicit NIO imports (#407)

Other Changes

• Improve HTTPClient tests (#405, #424, #426)
• Various CI fixes (#408, #410, #414, #436)