Replace Kubectl instructions with reference to authoritative page

This page previously included instructions to use curl to download and install
Kubectl via http, rather than with https. This exposed the end user to
man-in-the-middle attacks.

Additionally, the instructions given here are slightly different from the
authoritative page at https://kubernetes.io/docs/getting-started-guides/kubectl/
- which covers useful things like getting the latest release and setting up tab
autocompletion.

Rather than just change 'http' to 'https' in the URLs here, I've updated the
minikube setup page to include a reference to the kubectl setup page.

docs/getting-started-guides/minikube.md

@@ -31,19 +31,7 @@ Minikube is a tool that makes it easy to run Kubernetes locally. Minikube runs a
 * Linux
     * [VirtualBox](https://www.virtualbox.org/wiki/Downloads) or [KVM](http://www.linux-kvm.org/) installation,
 * VT-x/AMD-v virtualization must be enabled in BIOS
-* `kubectl` must be on your path. To install kubectl:
+* `kubectl` See the [kubectl installation instructions](/docs/getting-started-guides/kubectl/) for more details.
-
-**Kubectl for Linux/amd64**
-
-```
-curl -Lo kubectl http://storage.googleapis.com/kubernetes-release/release/{{page.version}}/bin/linux/amd64/kubectl && chmod +x kubectl && sudo mv kubectl /usr/local/bin/
-```
-
-**Kubectl for OS X/amd64**
-
-```
-curl -Lo kubectl http://storage.googleapis.com/kubernetes-release/release/{{page.version}}/bin/darwin/amd64/kubectl && chmod +x kubectl && sudo mv kubectl /usr/local/bin/
-```
 
 ### Instructions