SINGA-266 Add Rafiki python toolkits   - change agent api to support genernal post request
SINGA-266 Add Rafiki python toolkits
  - change agent api to support genernal post request

nusdbsystem/incubator-singa,nudles/incubator-singa,nudles/incubator-singa,ijingo/incubator-singa,kaiping/incubator-singa,ijingo/incubator-singa,nusdbsystem/incubator-singa,kaiping/incubator-singa,nudles/incubator-singa,nudles/incubator-singa,ijingo/incubator-singa,nusdbsystem/incubator-singa,apache/incubator-singa,apache/incubator-singa,ijingo/incubator-singa,apache/incubator-singa,nusdbsystem/incubator-singa,apache/incubator-singa,ijingo/incubator-singa,apache/incubator-singa,kaiping/incubator-singa,nudles/incubator-singa,kaiping/incubator-singa,nusdbsystem/incubator-singa,kaiping/incubator-singa