Move contribution information to separate file

CONTRIBUTING.md

@@ -0,0 +1,45 @@
+### Where to Start
+
+In order to contribute to IdeaVim you should have some understanding of Java or [Kotlin](https://kotlinlang.org/).
+
+See also these docs on the IntelliJ API:
+
+* [IntelliJ architectural overview](http://confluence.jetbrains.com/display/IDEADEV/IntelliJ+IDEA+Architectural+Overview)
+* [IntelliJ plugin development resources](http://confluence.jetbrains.com/display/IDEADEV/PluginDevelopment)
+
+You can start by picking relatively simple tasks that are tagged with
+[#patch_welcome](https://youtrack.jetbrains.com/issues/VIM?q=%23patch_welcome%20%23Unresolved%20sort%20by:%20votes%20)
+in the issue tracker.
+
+
+### Development Environment
+
+1. Fork IdeaVim on GitHub and clone the repository on your local machine.
+
+2. Import the project from existing sources in IntelliJ IDEA 2018.1 or newer (Community or
+   Ultimate) using "File | New | Project from Existing Sources..." or "Import
+   Project" from the start window.
+
+    * In the project wizard select "Import project from external model | Gradle"
+
+    * Select your Java 8+ JDK as the Gradle JVM, leave other parameters unchanged
+
+3. Run your IdeaVim plugin within IntelliJ via a Gradle task
+
+    * Select "View | Tool Windows | Gradle" tool window
+    
+    * Launch "ideavim | intellij | runIde" from the tool window
+
+4. Run IdeaVim tests via a Gradle task
+
+    * Select "View | Tool Windows | Gradle" tool window
+    
+    * Launch "ideavim | verification | test" from the tool window
+
+5. Build the plugin distribution by running `./gradlew clean buildPlugin` in the
+   terminal in your project root.
+
+    * The resulting distribution file is build/distributions/IdeaVim-VERSION.zip
+
+    * You can install this file using "Settings | Plugins | Install plugin
+      from disk"

README.md

@@ -56,9 +56,11 @@ Get an Early Access
 -------------------
 
 Would you like to try new features and fixes? Join the Early Access Program and
-receive EAP builds as updates! Add this URL to "Settings | Plugins |
+receive EAP builds as updates!  
-Browse Repositories | Manage Repositories":
+
-[https://plugins.jetbrains.com/plugins/eap/ideavim](https://plugins.jetbrains.com/plugins/eap/ideavim)
+Add [https://plugins.jetbrains.com/plugins/eap/ideavim](https://plugins.jetbrains.com/plugins/eap/ideavim) to:  
+_IJ versions 2018.3 and newer:_ "Settings | Plugins | Cog icon | Manage Plugin Repositories"  
+_IJ versions 2018.2 and older:_ "Settings | Plugins | Browse Repositories | Manage Repositories"
 
 See [the changelog](CHANGES.md) for the list of hot unreleased features.
 
@@ -182,52 +184,7 @@ For example, here `\r` is mapped to the Reformat Code action:
 Contributing
 ------------
 
-### Where to Start
+See [CONTRIBUTING.md](CONTRIBUTING.md)
-
-In order to contribute to IdeaVim you should have some understanding of Java.
-
-See also these docs on the IntelliJ API:
-
-* [IntelliJ architectural overview](http://confluence.jetbrains.com/display/IDEADEV/IntelliJ+IDEA+Architectural+Overview)
-* [IntelliJ plugin development resources](http://confluence.jetbrains.com/display/IDEADEV/PluginDevelopment)
-
-You can start by picking relatively simple tasks that are tagged with
-[#patch_welcome](http://youtrack.jetbrains.com/issues/VIM?q=%23patch_welcome)
-in the issue tracker.
-
-
-### Development Environment
-
-1. Fork IdeaVim on GitHub and clone the repository on your local machine.
-
-2. Import the project from existing sources in IntelliJ IDEA 2018.1 or newer (Community or
-   Ultimate) using "File | New | Project from Existing Sources..." or "Import
-   Project" from the start window.
-
-    * In the project wizard select "Import project from external model | Gradle"
-
-    * Select your Java 8+ JDK as the Gradle JVM, leave other parameters unchanged
-
-3. Run your IdeaVim plugin within IntelliJ via a Gradle task
-
-    * Select "View | Tool Windows | Gradle" tool window
-    
-    * Launch "ideavim | intellij | runIde" from the tool window
-
-4. Run IdeaVim tests via a Gradle task
-
-    * Select "View | Tool Windows | Gradle" tool window
-    
-    * Launch "ideavim | verification | test" from the tool window
-
-5. Build the plugin distribution by running `./gradlew clean buildPlugin` in the
-   terminal in your project root.
-
-    * The resulting distribution file is build/distributions/IdeaVim-VERSION.zip
-
-    * You can install this file using "Settings | Plugins | Install plugin
-      from disk"
-
 
 Authors
 -------