allow showing tips as messages

[naquad]

Thank you for a very intersting plugin! Everything is fine, but I found window-based tip display to be a bit confusing, I think it it would be more natural to display them as messages.

In this commit I've added a new option: g:fortune_display_in_window which is 1 by default (current behavior), but if you set it to 0 then tips will be displayed as messages.

[hobbestigrou]

Thanks @naquad for your contribution and sorry for the time of my answer. Can you only add little documentation please.

[hobbestigrou]

Sorry @naquad can you see to add the documentation please.

[naquad]

ok, this evening I'll add docs and maybe rename the var

[hobbestigrou]

Ok for me, I agree.