remove unused property
add `jsonrpc` property
fix id is null on request's id not found
change response error format
Revert "change response error format"

This reverts commit 2ac1355d52b6e02722c88dcfba82f9967d82d4a6.
fix code for reviewed
Merge pull request #61 from horiuchi/response-format

Remove unused property in response object.