To fix #20644

Added a note on development kit for Windows Users.  This is required as Windows users can get frustrated when their first rails project creation would fail as some native gem won't get built.

guides/source/getting_started.md

@@ -23,7 +23,8 @@ application from scratch. It does not assume that you have any prior experience
 with Rails. However, to get the most out of it, you need to have some
 prerequisites installed:
 
-* The [Ruby](https://www.ruby-lang.org/en/downloads) language version 2.2.2 or newer.
+* The [Ruby](https://www.ruby-lang.org/en/downloads) language version 2.2.2 or newer. 
+* Right version of [Development Kit](http://rubyinstaller.org/downloads/), if you are using Windows
 * The [RubyGems](https://rubygems.org) packaging system, which is installed with Ruby
   versions 1.9 and later. To learn more about RubyGems, please read the [RubyGems Guides](http://guides.rubygems.org).
 * A working installation of the [SQLite3 Database](https://www.sqlite.org).