Add markdownlint config file, address some issues

Mostly related to whitespace (newlines / trailing),
lots of issues remaining to fix in the docs directory.

As usual linting takes most effort when you start,
but from there it is easier to keep code and docs clean.

.markdownlint.json

+{
+  "no-inline-html": false,
+  "no-trailing-punctuation": false,
+  "ul-style": false,
+  "line_length": false
+}

README.md

@@ -13,7 +13,7 @@
 
 ## What is minikube?
 
-minikube implements a local Kubernetes cluster on macOS, Linux, and Windows. 
+minikube implements a local Kubernetes cluster on macOS, Linux, and Windows.
 
 <img src="https://github.com/kubernetes/minikube/raw/master/images/start.jpg" width="800">
 
@@ -31,7 +31,7 @@ Our [goal](https://github.com/kubernetes/minikube/blob/master/docs/contributors/
 
 minikube runs the official stable release of Kubernetes, with support for standard Kubernetes features like:
 
-* [LoadBalancer](https://github.com/kubernetes/minikube/blob/master/docs/tunnel.md) - using `minikube tunnel` 
+* [LoadBalancer](https://github.com/kubernetes/minikube/blob/master/docs/tunnel.md) - using `minikube tunnel`
 * Multi-cluster - using `minikube start -p <name>`
 * NodePorts - using `minikube service`
 * [Persistent Volumes](https://github.com/kubernetes/minikube/blob/master/docs/persistent_volumes.md)
@@ -56,7 +56,7 @@ As well as developer-friendly features:
 
 ## Community
 
-minikube is a Kubernetes [#sig-cluster-lifecycle](https://github.com/kubernetes/community/tree/master/sig-cluster-lifecycle)  project. 
+minikube is a Kubernetes [#sig-cluster-lifecycle](https://github.com/kubernetes/community/tree/master/sig-cluster-lifecycle)  project.
 
 * [**#minikube on Kubernetes Slack**](https://kubernetes.slack.com) - Live chat with minikube developers!
 * [minikube-users mailing list](https://groups.google.com/forum/#!forum/minikube-users)
@@ -81,7 +81,7 @@ See the [installation guide](https://kubernetes.io/docs/tasks/tools/install-mini
   * using [chocolatey](https://chocolatey.org/) `choco install minikube`
   * manually: Download and run the [installer](https://storage.googleapis.com/minikube/releases/latest/minikube-installer.exe)
 
-* *Linux* 
+* *Linux*
   * Requires either the [kvm2 driver](https://github.com/kubernetes/minikube/blob/master/docs/drivers.md#kvm2-driver) (recommended), or VirtualBox
   * VT-x/AMD-v virtualization must be enabled in BIOS
   * manually:  `curl -LO https://storage.googleapis.com/minikube/releases/latest/minikube-linux-amd64 && sudo install minikube-linux-amd64 /usr/local/bin/minikube`