Merge pull request #11 from xiangli-cmu/master

add remove instance.
Merge pull request #12 from xiangli-cmu/master

move proxy to service
Merge pull request #13 from xiangli-cmu/master

add a roundrobin selector
define policy type
refine naming
Merge pull request #14 from fengjingchao/dev

define policy type
Add Router API
Merge pull request #16 from fengjingchao/dev

Add Router API CreateService
rpc example
Merge pull request #17 from xiangli-cmu/rpc_example

rpc example
finish RPC and refactor router
Merge pull request #18 from fengjingchao/dev

finish rpc interface
controller init
Merge pull request #19 from xiangli-cmu/controller

controller init
finish CRouter
Merge pull request #20 from fengjingchao/dev

finish CRouter
feat(router) add service type for instance