Ensuring all HTTP connections are properly closed

[nathankurtyka]

Hello, and great work on this library!

We've recently discovered an HTTP connection leak can occur under network edge conditions.

This is a pull request that ensures that "... that the entity content has been fully consumed and the underlying stream has been closed" (https://hc.apache.org/httpcomponents-client-4.5.x/tutorial/html/fundamentals.html)

Specifically, the code below reads the full response (while still preserving the code's dependency on accessing the response InputStream), as well as guaranteeing that the response is closed. Both of these steps are important, and are consistent with the HttpClient recommendations.

Let me know if you have any questions! We've been running these modifications in Production for several days now and have not seen the connection leak since.

[jingming]

@nathankurtyka There appears to be a compilation error in your code https://travis-ci.org/twilio/twilio-java/builds/225457155

[nathankurtyka]

@jingming - D'oh.. sorry about that. The branch has been fixed.

Let me know if you have any questions! In debugging the leak I had to get somewhat deep into HttpClient, and I'd be happy to save you that time.

[jingming]

@nathankurtyka great, thanks for the PR! We will take a look at this further as soon as we can, so please bear with us!