Extrapolating the bcc address from the envelope

Will create a pull request on Griddler now that has minimal changes and depends on this parser to actually get the bcc. Hopefully this will help.

In response to this: 
https://github.com/thoughtbot/griddler/issues/168
no if/unless surprises, please. Can this be restructured to be one big conditional, or a nested one?

```
if address.present?
  if addresses.is_a? Array
    bcc -= addresses
  elsif bcc.present?
    bcc.delete(addresses)
  end
  bcc
end
```

And actuall Array has `#delete`, so we could probably do something like

```
if addresses.present? && addresses.respond_to?(:delete)
  addresses.delete(bcc)
end
bcc
```