fix http proxy support in spring4

Hi,
This is a workaround waiting for Spring to fix proxy support. In RequestFactory, I set a default route planner to handle proxy otherwise proxy is ignored. I've also updated test case to explicitly show if a restTemplate use a proxy or not.

https://jira.spring.io/browse/SPR-12335 When using HttpComponentsClientHttpRequestFactory, setting a proxy through RequestConfig should not be ignored.

Regards,
 Olivier