readme and build improvements (scala#33)

readme and build improvements

Author: lrytz

README.md

@@ -2,6 +2,14 @@
 
 This module provides various additions to the Scala 2.13 standard collections.
 
+## Usage
+
+If you're using sbt, you can add the dependency as follows:
+
+```
+libraryDependencies += "org.scala-lang.modules" %% "scala-collection-contrib" % "0.1.0"
+```
+
 ## New collection types
 
 - `MultiSet` (both mutable and immutable)

build.sbt

@@ -1,24 +1,21 @@
 import ScalaModulePlugin._
 
 scalaModuleSettings
+scalaModuleSettingsJVM
 
 name := "scala-collection-contrib"
-version := "0.1.0-SNAPSHOT"
+version := "0.1.1-SNAPSHOT"
 
-scalaVersionsByJvm in ThisBuild := {
-  val v213 = "2.13.0"
-  Map(
-    8 -> List(v213 -> true),
-    11 -> List(v213 -> false),
-    12 -> List(v213 -> false))
-}
+crossScalaVersions in ThisBuild := Seq("2.13.0")
 
 scalacOptions ++= Seq("-opt-warnings", "-language:higherKinds", "-deprecation", "-feature", "-Xfatal-warnings")
 scalacOptions in (Compile, doc) ++= Seq("-implicits", "-groups")
 
 testOptions += Tests.Argument(TestFrameworks.JUnit, "-q", "-v", "-s", "-a")
 parallelExecution in Test := false  // why?
 
+mimaPreviousVersion := Some("0.1.0")
+
 homepage := Some(url("https://github.com/scala/scala-collection-contrib"))
 licenses := Seq("Apache-2.0" -> url("https://www.apache.org/licenses/LICENSE-2.0"))