All exceptions — including signals — are caught during an observation

`observation.rb` does this:

```ruby
def initialize(name, experiment, &block)
...

begin
@value = block.call
rescue Object => e
@exception = e
end

...
end
```

Which is a [well](http://daniel.fone.net.nz/blog/2013/05/28/why-you-should-never-rescue-exception-in-ruby/) [documented](http://www.mikeperham.com/2012/03/03/the-perils-of-rescue-exception/) [anti-pattern](https://robots.thoughtbot.com/rescue-standarderror-not-exception). In particular, it means that any signals (eg. ``) will be treated as-if they were just an error in the candidate code (which usually means logging and ignoring).

Note: There's no difference between `rescue Object` and `rescue Exception` because raising a non-exception (eg. a string) will either raise a `` or a ``.

I think the standard pattern — `rescue StandardError` — is correct here. That will catch everything except `SignalException`s and other things which aren't meant to be dealt-with as part of standard error handling.

Although users could filter-out all non-StandardError Exceptions themselves, this feels like a footgun (since signals will be relatively rare — especially in development — most users won't notice any problems until they happen in production).

Bắt đầu trong observation.rb tại phương thức initialize và kiểm tra rescue quanh block.call. Thay đổi cách xử lý ngoại lệ theo yêu cầu để các signal không bị coi là lỗi của mã ứng viên, sau đó xác minh rằng các lỗi chuẩn vẫn được bắt mà không nuốt các signal.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.