Add stacktrace to app.chain

[astashov]

It is really useful sometimes to have access to it.

A possible use case - integration with error aggregators, like Airbrake or Rollbar, so you could send errors with stacktraces to these services

[cgarciae]

Could you please all try to add this to the 0.6 branch? Its beta but all efforts are currently focused on that branch.

[astashov]

Sure

[cgarciae]

Thanks. Actually I think @luizmineo uses the stack_trace package in 0.6 but in my experience error where reported better in 0.5.

[astashov]

Closing in favor of https://github.com/redstone-dart/redstone/pull/128