Fix master/osx builds: switch to kubecfg 0.7.2

kubecfg 0.7.1 was never released for osx, but our travis testing
failed to notice because it was still using the previously cached
kubecfg binary.

a) Change to kubecfg 0.7.2
b) Always use the expected version of kubecfg so an error like this
   won't slip through CI testing again
c) Ditto for minikube, kubectl

.travis.yml

@@ -43,15 +43,21 @@ install:
   - go build -i ./...
   - |
     if [ "$INT_KVERS" != "" ]; then
-      if ! which minikube; then
-        wget -O minikube \
-           https://storage.googleapis.com/minikube/releases/v0.25.0/minikube-$(go env GOOS)-$(go env GOARCH)
-        install -m 755 minikube $GOPATH/bin/minikube
+      v=0.25.0
+      if ! which minikube-$v; then
+        wget -O $GOPATH/bin/minikube-$v \
+           https://storage.googleapis.com/minikube/releases/v$v/minikube-$(go env GOOS)-$(go env GOARCH)
+        chmod +x $GOPATH/bin/minikube-$v
       fi
-      if ! which kubectl; then
-        wget https://storage.googleapis.com/kubernetes-release/release/$INT_KVERS/bin/$(go env GOOS)/$(go env GOARCH)/kubectl
-        install -m 755 kubectl $GOPATH/bin/kubectl
+      ln -sf minikube-$v $GOPATH/bin/minikube
+
+      v=$INT_KVERS
+      if ! which kubectl-$v; then
+        wget -O $GOPATH/bin/kubectl-$v https://storage.googleapis.com/kubernetes-release/release/$v/bin/$(go env GOOS)/$(go env GOARCH)/kubectl
+        chmod +x $GOPATH/bin/kubectl-$v
       fi
+      ln -sf kubectl-$v $GOPATH/bin/kubectl
+
       mkdir -p $(dirname $KUBECONFIG)
       touch $KUBECONFIG
       sudo -E $GOPATH/bin/minikube start --vm-driver=none \
@@ -61,10 +67,12 @@ install:
       go get github.com/onsi/ginkgo/ginkgo
     fi
   - |
-    if ! which kubecfg; then
-      wget -O $GOPATH/bin/kubecfg https://github.com/ksonnet/kubecfg/releases/download/v0.7.1/kubecfg-$(go env GOOS)-$(go env GOARCH)
-      chmod +x $GOPATH/bin/kubecfg
+    v=0.7.2
+    if ! which kubecfg-$v; then
+      wget -O $GOPATH/bin/kubecfg-$v https://github.com/ksonnet/kubecfg/releases/download/v$v/kubecfg-$(go env GOOS)-$(go env GOARCH)
+      chmod +x $GOPATH/bin/kubecfg-$v
     fi
+    ln -sf kubecfg-$v $GOPATH/bin/kubecfg
   - git clone --depth=1 https://github.com/ksonnet/ksonnet-lib.git
   - export KUBECFG_JPATH=$PWD/ksonnet-lib