Added support for skip_bugsnag flag on exceptions

[Cawllec]

Adds supports for setting a skip_bugsnag flag on exceptions to allow re-raising after notifying as requested in #345

[coveralls]

Coverage increased (+0.07%) to 76.931% when pulling 118e9ff on cawllec/allow-re-raise-errors into bbef3cc on master.

[snmaynard]

Why add this rather than advise the use of bugsnag_meta_data? This will report the exception as handled, when infact it is unhandled.

[Cawllec]

For the particular use case of the guy in #345 just using the bugsnag_meta_data wouldn't necessarily solve his problem, whereas this allows specific individual exceptions to be skipped if required.

[snmaynard]

It would solve his problem - he could attach the metadata and then reraise

[javierjulio]

@snmaynard when you refer to bugsnag_meta_data, do you mean I should do the following to avoid double notification if I end up re-raising the error?

rescue SomeStandardErrorClass => error
  Bugsnag.notify(error, { skip_bugsnag: true })
  raise error
end

The Bugsnag docs state setting a skip_bugsnag property on an error class which I realize now doesn't make any sense since where I tend to do this type of handling is for third party code (e.g. API client library) where I can't set that. The method is not defined. Stupid mistake on my part.

Would the metadata approach work in the example I gave? Should the docs example be updated?

[snmaynard]

I think you would want to do something like this,

rescue SomeStandardErrorClass => error
  Bugsnag.notify(error)
  error.define_singleton_method(:skip_bugsnag) {true}
  raise error
end