RequestBin is deprecated, replace with new service

[beriberikix]

We recommend that developers use RequestBin to test Webhooks but the service is now turned off.

Can we find an alternative service to recommend to users?

[monkbroc]

It would be cool to spin up an instance of https://github.com/Kong/mockbin to https://mockbin.particle.io

We could set it up so it only accepts requests from the Particle webhook service to avoid abuse (the reason that RequestBin shut down)

[beriberikix]

That would be awesome!