Each AWS::Core::Http::NetHttpHandler instance gets its own pool.

Clients that share http handlers will continue sharing pools.
Added #exists? method to AWS::EC2::VPC.
Updated AWS::CloudFront::Client to the 2014-01-31 API version.
Updated ELB API model.
Updated AWS::Kinesis::Client docs.
Updated connection pool specs for the recent construction change.
Bump version to v1.36.0