Report exceptions occurring in Rake tasks and runner commands

[TylerRick]

Resolves #369

[TylerRick]

All right, I think this is ready for review and/or merge now.

I guess we should update the Readme, too, and mention (or change) the fact that you need to:

• Add require 'exception_notification/rails' below Bundler.require in your config/application.rb if you want to enable these behaviors.
• Requiring it from an initializer is too late, because the rake_tasks callbacks have already been fired by that point.
• ('exception_notification/rails' doesn't appear to be auto-required. Should it be?)
• You can also require require 'exception_notification/rake' only, if for whatever reason you only want to enable that portion.

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I didn't add tests for the runner portion, because that would require having a Rails app in our test environment, and I see that test/dummy, which used to include such an app, has been removed. (But I did manually test it from my app.)

If that is desired, could you please advise how you would prefer a Rails app to be added in tests? Should we manually generate one and add it back as test/dummy? It seems like that would suffer from bit rot and would be one more thing we'd need to maintain. Or should we add another gem that does some of that for us? (Don't know of one off-hand.)

Or should we look into doing it how they do it in railties/test/application/runner_test.rb or railties/test/commands/runner_test.rb, where they have these handy helpers like build_app (to generate a fresh Rails app on the fly) and

output = rails("runner", "puts 'hello world", allow_failure: true)       

? Those appear to come from their test/isolation/abstract_unit.rb file, which unfortunately is not included with the railties gem itself, so it seems that we would have to copy and paste that into our gem if we wanted to use it. (And even then, it might require other test dependencies...)

[smartinez87]

Thank you @TylerRick for the PR, it looks great!

As you say, having test/dummy app was painful to maintain, so no need to go down that path again.
Can you please add the needed change in the Readme for this?

[TylerRick]

Okay, I took a stab at updating the docs!

I also added a note to the generated initializer (for people who don't read docs).

[smartinez87]

thank you @TylerRick, amazing job!