Issue Summary

Because sendgrid/java-http-client depends on org.apache.httpcomponents/httpcore, this library is necessary under google appengine in order to stay under socket connection quotas:
https://github.com/sendgrid/sendgrid-google-java

But it looks like that library is soon to be very out of date with the latest sendgrid apis. It would be great if java-http-client could remove that dependency and just use the built in java http connection apis directly so that the official sendgrid-java library would work in all scenarios.