Note which MRI versions Friction supports (due to rafalchmiel/friction#11)

Rafal Chmiel · Rafal Chmiel · commit 8642db715362 · 2014-04-17T16:11:29.000+01:00
diff --git a/README.md b/README.md
@@ -416,6 +416,8 @@ If you want people to use and contribute to your project, you need to start by a
 
 [![Friction output](http://i.imgur.com/4EgpWo4.png)](https://github.com/rafalchmiel/friction)
 
+*Friction supports MRI 2.1.0, MRI 2.0.0, and MRI 1.9.3.*
+
 ### Contributing Guidelines
 Adding a `CONTRIBUTING` file to the root of your repository will add a link to your file when a contributor creates an Issue or opens a Pull Request.
 
