Add links to slack, googlegroup, repo, book resources to GitBook and …

…README.md

Also add message about sharing the book.

Fixes #174
Fixes #173

README.md

@@ -29,6 +29,14 @@ See the [Getting Started](http://book.kubebuilder.io/quick_start.html) documenta
 
 ![Quick Start](docs/gif/quickstart.gif)
 
+## Resources
+
+GitBook: [book.kubebuilder.com](http://book.kubebuilder.com)
+GitHub Repo: [kubernetes-sigs/kubebuilder](https://github.com/kubernetes-sigs/kubebuilder)
+Slack channel: [#kubeuilder](http://slack.k8s.io/#kubebuilder)
+Google Group: [kubebuilder@googlegroups.com](https://groups.google.com/forum/#!forum/kubebuilder)
+Planned Work: [Sprint Dashboard](https://github.com/kubernetes-sigs/kubebuilder/projects/1)
+
 ## Motivation
 
 Building Kubernetes tools and APIs involves making a lot of decisions and writing a lot of boilerplate.

docs/book/README.md

@@ -4,6 +4,8 @@ This book is being actively developed.
 
 **Note:** Impatient readers head straight to [Quick Start](quick_start.md).
 
+*To share this book use the icons in the top-right of the menu.*
+
 ## Who is this for
 
 #### Users of Kubernetes
@@ -39,6 +41,14 @@ Including:
     - How to use Declarative vs Webhook Validation
     - How to implement API versioning
 
+## Resources
+
+GitBook: [book.kubebuilder.com](http://book.kubebuilder.com)
+GitHub Repo: [kubernetes-sigs/kubebuilder](https://github.com/kubernetes-sigs/kubebuilder)
+Slack channel: [#kubeuilder](http://slack.k8s.io/#kubebuilder)
+Google Group: [kubebuilder@googlegroups.com](https://groups.google.com/forum/#!forum/kubebuilder)
+Planned Work: [Sprint Dashboard](https://github.com/kubernetes-sigs/kubebuilder/projects/1)
+
 ## Navigating this book
 
 This section describes how to use the navigation elements of this book