Upgrade docs (#1182)

* remove table of contents

* remove more hard-coded table of contents

* remove comparisons, rewrite "why" section to be more general

* update intro

docs/walkthroughs/Readme.md

@@ -1,15 +0,0 @@
-
-# Walkthroughs
-
-These walkthroughs introduce you to the different parts of Slate in a step-by-step way that build on each other, perfect for getting started. We recommend reading them in order, start to finish!
-
-- [Installing Slate](./installing-slate.md)
-- [Using the Bundled Source](./using-the-bundled-source.md)
-- [Adding Event Handlers](./adding-event-handlers.md)
-- [Defining Custom Block Nodes](./defining-custom-block-nodes.md)
-- [Applying Custom Formatting](./applying-custom-formatting.md)
-- [Using Plugins](./using-plugins.md)
-- [Saving to a Database](./saving-to-a-database.md)
-- [Saving and Loading HTML Content](./saving-and-loading-html-content.md)
-
-_If you have an idea for a walkthrough, or notice something that isn't clear, submit a pull request!_