Pin mail-parser test dep to the latest version so tests work correctly.
Pin mail-parser test dep to the latest version so tests work correctly.

StackStorm/st2,Plexxi/st2,nzlosh/st2,nzlosh/st2,StackStorm/st2,nzlosh/st2,StackStorm/st2,Plexxi/st2,nzlosh/st2,Plexxi/st2,Plexxi/st2,StackStorm/st2