upgrade version of yarn used by travis
upgrade version of yarn used by travis
Jigsaw-Code/outline-client,Jigsaw-Code/outline-client,Jigsaw-Code/outline-client,Jigsaw-Code/outline-client,Jigsaw-Code/outline-client,Jigsaw-Code/outline-client,Jigsaw-Code/outline-client,Jigsaw-Code/outline-client,Jigsaw-Code/outline-client,Jigsaw-Code/outline-client