public HttpRequest body(final AtomicReference<String> output, final String charset) throws HttpRequestException {
    output.set(body(charset));
    return this;
  }
Get the response body as a {@link String} and set it as the value of the
given reference.

@param output
@param charset
@return this request
@throws HttpRequestException
lib/src/main/java/com/github/kevinsawicki/http/HttpRequest.java