Fetch fix for crypto/ssh bug 18861

This pulls the fix into travis build to tests can continue while they
get this bug merged upstream.

golang/go#18861

.travis.yml

@@ -19,6 +19,7 @@ addons:
 install:
   - go get -t -v ./...
   - ssh-keygen -t rsa -q -P "" -f $HOME/.ssh/id_rsa
+  - cd $GOPATH/src/golang.org/x/crypto && git fetch https://go.googlesource.com/crypto refs/changes/55/36055/1 && git checkout FETCH_HEAD
 
 script:
   - go test -integration -v ./...