- Why?
This would allow a user of the API to rescue for example in an ApplicationJob and retry when the time has passed, rather than sleeping.

```
def perform
  req.execute(uri, token: 'test-token')
rescue Intercom::RateLimitExceeded => e
  self.class.perform_at(e.rate_limit_details[:reset_at])
end
```

- How?

* Adds attr_accessor to RateLimitExceeded on errors.rb
* Intercom::Request#execute rescue block injects the  @rate_limit_details before raising the exception