Bump the http client to apache http client 5

The custom http client used by `sendgrid-java` is out of date and there is an open issue and a PR (I raised) to update it, but it doesn't seem like that repo is monitored maybe.

If someone that tends to this repo could take a look that would be helpful! 

Issue: https://github.com/sendgrid/java-http-client/issues/147
PR: https://github.com/sendgrid/java-http-client/pull/148

