User tokens have moved

[Jack Ellenberger]

Looks like a recent Slack update moved the api_token from being in a big string / array of strings / whatever it was to a proper json object, still called boot_data.

So instead of doing a regex search we should be able to just access it as window.boot_data.api_token :nice:

[Aarni Koskela]

#10 fixes this.