Issue title: Custom notifications on process restarts
 Issue body: Hi

how can i add custom body to the message that being sent on restarts events etc..

 Comments: 
 Comment 0: you mean mail notify?

you should do something like this:

```
Ey38d1:d2b4:3d06:83e8:96a5:8c2:893d:aba5Notify38d1:d2b4:3d06:83e8:96a5:8c2:893d:aba5Mail
class Ey38d1:d2b4:3d06:83e8:96a5:8c2:893d:aba5Notify38d1:d2b4:3d06:83e8:96a5:8c2:893d:aba5Mail
  def message_body
     "my custom body"
  end
end

Eye.app :bla do
  notify ...
end
```

 Comment 1: You're awesome !!! Thank you!

Ami mahloof 

> On 28 בספט 2014, at 18:31, kostya fwagner@example.net wrote:
> 
> you mean mail notify?
> 
> you should do something like this:
> 
> Ey38d1:d2b4:3d06:83e8:96a5:8c2:893d:aba5Notify38d1:d2b4:3d06:83e8:96a5:8c2:893d:aba5Mail
> class Ey38d1:d2b4:3d06:83e8:96a5:8c2:893d:aba5Notify38d1:d2b4:3d06:83e8:96a5:8c2:893d:aba5Mail
>   def message_body
>      "my custom body"
>   end
> end
> 
> Eye.app :bla do
>   notify ...
> end
> —
> Reply to this email directly or view it on GitHub.

{'source': 'GithubIssues', 'repo_name_with_owner': 'kostya/eye', 'issue_id': 44232285, 'repo_stars': 1180.0}