public static Builder newBuilder() {
        return new Builder();
    }
Test if the request is retriable. If the request is
a {@link Verb#GET} and {@link Builder#setRetriable(boolean)}
is not called, returns true. Otherwise, returns value passed in
{@link Builder#setRetriable(boolean)}
ribbon-httpclient/src/main/java/com/netflix/client/http/HttpRequest.java