SSR Support

Hello,

I am currently developing a server-side rendered app using [NextJS](https://nextjs.org) that fetches data in the backend and then generates presentations based on this data. It would be great if I could use your library but unfortunately, I always run into the following error:

```
self is not defined
ReferenceError: self is not defined
at Object. (/Users/lukasgabsi/Projects/sprint-slides-generator/node_modules/broadcastchannel-polyfill/index.js:85:4)
at Module._compile (internal/modules/cjs/loader.js:816:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:827:10)
at Module.load (internal/modules/cjs/loader.js:685:32)
at Function.Module._load (internal/modules/cjs/loader.js:620:12)
at Module.require (internal/modules/cjs/loader.js:723:19)
at require (internal/modules/cjs/helpers.js:14:16)
at Object. (/Users/lukasgabsi/Projects/sprint-slides-generator/node_modules/spectacle/lib/components/deck/presenter-deck.js:32:1)
at Module._compile (internal/modules/cjs/loader.js:816:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:827:10)
at Module.load (internal/modules/cjs/loader.js:685:32)
at Function.Module._load (internal/modules/cjs/loader.js:620:12)
at Module.require (internal/modules/cjs/loader.js:723:19)
at require (internal/modules/cjs/helpers.js:14:16)
at Object. (/Users/lukasgabsi/Projects/sprint-slides-generator/node_modules/spectacle/lib/components/deck/index.js:24:45)
at Module._compile (internal/modules/cjs/loader.js:816:30)
```

I am aware of the solution that was discussed in #257 using a custom history object but I can't find anything about that in the docs. Is this still a thing in version 6? It would be great if SSR support was guaranteed out of the box.

Best regards!