Make the 'stdout/stderr/exit code' available during exceptions

An error is raised when a `ssh_execute` command returns an exit code greater than 0. This change allows use to capture that information in a rescue call.

:fire: :fire_engine: 

Example:

```
begin
  # ... do something
rescue Veewee::Provider::Core::Helper::SshResult => result
  puts result.stdout
end
```