Idea: ensure rake integration is enabled when rescue_rake_exceptions is true

[Nitrodist]

I ran into a bit of an issue where I thought I had enabled the rake integration in my ruby project but it turns out that airbrake wasn't sending the exceptions to airbrake (even though I had airbrake required and rescue_rake_exceptions was set true).

As it turns out (and in the cucumber spec), one must require airbrake/rake_handler for it to work. Without this required, then the exceptions won't be sent to Airbrake (silently not sending).

Given the nature of rake tasks, I think that if the setting for rescuing from rake exceptions is set to true, then we should ensure that the rake integration is enabled via one or two ways:

1. Raise an exception at run-time if the airbrake/rake_handler isn't loaded when rescue_rake_exceptions is set to true
2. Automatically load airbrake/rake_handler after rescue_rake_exceptions is enabled.

I'm willing to do the work to get this going, but I'd like to know which one is the appropriate way to do it before working on it.

[alif]

Either approach seems like it might be acceptable.
We're discussing this one internally. We'll let you know soon!

[alif]

I think option 1. is the best. It's less intrusive and less complicated. I'll keep an eye out for your PR.

[Nitrodist]

It lives. #294