Won't install dependencies on linux platform

`reprocessing-scripts` depends on `ios-deploy` which won't install on linux.

```
~/D/reprocessing-example-cross-platform (mstr) npm i
npm WARN reprocessing-example-cross-platform@1.0.3 No repository field.

npm ERR! code EBADPLATFORM
npm ERR! notsup Unsupported platform for ios-deploy@1.9.2: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})
npm ERR! notsup Valid OS: darwin
npm ERR! notsup Valid Arch: any
npm ERR! notsup Actual OS: linux
npm ERR! notsup Actual Arch: x64

npm ERR! A complete log of this run can be found in:
npm ERR! /home/skrat/.npm/_logs/2018-04-10T19_36_59_467Z-debug.log
```

Also, [the article](https://jaredforsyth.com/posts/making-a-cross-platform-mobile-game-in-reason-ocaml/) doesn't mention anything about getting the `rsb` command which apparently is needed.

Reproduce the failure with `npm i` on Linux using the command and error shown. Check how `reprocessing-scripts` brings in `ios-deploy` and how the linked article introduces the `rsb` command; done means Linux dependency installation works and the setup instructions explain obtaining `rsb`.

Written by the indexing model from the issue text.