travis: workaround go-get-insecure for rsc.io/pdf
while the go get rsc.io/pdf
failure is fixed upstream
(rsc/pdf#4), check out manually the repository from github and put it
in the correct place under $GOPATH.
while the go get rsc.io/pdf
failure is fixed upstream
(rsc/pdf#4), check out manually the repository from github and put it
in the correct place under $GOPATH.