Address feedback

Author: olafurpg

README.md

@@ -11,7 +11,7 @@ To use this library, add the following to your build.sbt:
 libraryDependencies += "org.scala-lang.modules" %% "scala-collection-compat" % "0.2.1"
 ```
 
-Version 0.2.1 is compatible with Scala 
+Version 0.2.1 is compatible with Scala 2.13.0-M5. For Scala 2.13.0-M4 you should use version 0.1.1.
 
 Note that there are multiple ways to cross-build projects, see https://github.com/scala/collection-strawman/wiki/FAQ#how-do-i-cross-build-my-project-against-scala-212-and-scala-213.
 
@@ -43,7 +43,7 @@ The migration rules use scalafix. Please see the [official installation instruct
 ```scala
 // project/plugins.sbt
 
-addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.9.0-RC1")
+addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.9.0")
 ```
 
 ### Collection213Upgrade
@@ -68,10 +68,12 @@ The `Collections213CrossCompat` rewrite upgrades to the 2.13 collections with th
 
 To cross-build for 2.12 and 2.11, the rewrite rule introduces a dependency on the scala-collection-compat module, which provides the syntax of 2.13 on 2.12 and 2.11. This enables you to write your library using the latest 2.13 collections API while still supporting users on an older Scala version.
 
+```scala
 // build.sbt
 scalafixDependencies += "org.scala-lang.modules" %% "scala-collection-migrations" % "0.2.1"
 libraryDependencies +=  "org.scala-lang.modules" %% "scala-collection-compat" % "0.2.1"
 scalacOptions ++= List("-Yrangepos", "-P:semanticdb:synthetics:on")
+```
 
 
 ```bash