Add a .dummy file in the changes directory to stop git from removing it

This file is here to keep git from removing the changes directory when

all the changes files have been merged.

"I'm Nobody! Who are you?

 Are you--Nobody--too?

 Then there's a pair of us!

 Don’t tell! they'd advertise--you know!

 How dreary--to be--Somebody!

 How public--like a Frog--

 To tell one's name--the livelong June--

 To an admiring Bog!"

    -- Emily Dickinson