Readme fixes [ci skip] 

Eurocrypt submission 

Update the README 

Version used for the CCS'20 submission 

Update the gRPC inports. <grpc++/*.h> has been deprecated in favor of <grpcpp/*.h>. Include all of grpcpp.h to avoid inclusion issues. Import <grpcpp/support/sync_stream.h> to get the streaming APIs.

Bump crypto-tk