Update README.md

Updates the README.md to remove references to prototyping, and updates the welcoming message to point people to the WordPress.org plugins repository for the latest Gutenberg release.

README.md

@@ -1,10 +1,10 @@
 # Gutenberg
 
-Prototyping since 1440.
+Printing since 1440.
 
 ![Text block](https://wpcoredesign.mystagingwebsite.com/gutenberg/gutenberg.png)
 
-This is the development and prototyping hub for the <a href="https://make.wordpress.org/core/2017/01/04/focus-tech-and-design-leads/">editor focus in core</a>. Gutenberg is the project name. Conversations and discussions take place in #core-editor on <a href="https://make.wordpress.org/chat/">the core WordPress Slack</a>. This is our kickoff goal:
+This is the development hub for the <a href="https://make.wordpress.org/core/2017/01/04/focus-tech-and-design-leads/">editor focus in core</a>. Gutenberg is the project name. If you want the latest release for your WordPress, <a href="https://wordpress.org/plugins/gutenberg/">download Gutenberg from the WordPress.org plugins repository</a>. Conversations and discussions take place in #core-editor on <a href="https://make.wordpress.org/chat/">the core WordPress Slack</a>. This is our kickoff goal:
 
 > The editor will endeavour to create a new page and post building experience that makes writing rich posts effortless, and has “blocks” to make it easy what today might take shortcodes, custom HTML, or “mystery meat” embed discovery. — Matt Mullenweg
 
@@ -15,7 +15,6 @@ WordPress already supports a large amount of "blocks", but doesn't surface them
 - <a href="https://make.wordpress.org/core/2017/01/17/editor-technical-overview/">Editor Technical Overview</a>
 - <a href="https://make.wordpress.org/core/2017/05/05/editor-how-little-blocks-work/">How Blocks Work</a>
 - <a href="https://wpcoredesign.mystagingwebsite.com/gutenberg/">Editor Mockups</a>
-- <a href="https://wordpress.github.io/gutenberg/">Prototypes</a>
 - <a href="https://github.com/Automattic/wp-post-grammar">WP Post Grammar Parser</a>
 - <a href="https://make.wordpress.org/core/tag/gutenberg/">Development updates on make.wordpress.org</a>