travis: move example tests to a separate run (#3143)
travis: move example tests to a separate run (#3143)

The example tests were causing travis timeout.
dfawley/grpc-go,grpc/grpc-go,grpc/grpc-go,menghanl/grpc-go,stanley-cheung/grpc-go,stanley-cheung/grpc-go,menghanl/grpc-go,dfawley/grpc-go