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