Make it Hapi 17 compatible

[Aconradty]

Hapi's breaking changes => https://github.com/hapijs/hapi/issues/3658 Fast merge would be appreciated !

[phenomax]

+1

[Elpayet]

+1

[Elpayet]

Seems like the PR has somehow already been merged. Adding a name when registrating the plugin may still be necessary:

await app.register({
  plugin : {
    name    : 'graphiqlHapiPlugin',
    register: graphiqlPlugin.plugin.register
  },
  options: {
    ...<plugin options here>
  }
})