Move the collectionContrib project to a collection-contrib subdirectory

This is a tentative to address #51

At least now, the `package` task builds a .jar file that contains .class files. The `publishLocal` task, however, still does not build a .jar file containing the .class files.

I’ve noticed that `collectionContribJS/publishLocal` builds a correct .jar file. The only difference between the JS and JVM projects is that the JVM project applies the `scalaModuleSettingsJVM` settings, which does something with sbt-osgi, which I didn’t dig into…

Author: julienrf

build.sbt

@@ -7,7 +7,7 @@ Test/sources := Nil
 lazy val collectionContrib = crossProject(JVMPlatform, JSPlatform)
   .withoutSuffixFor(JVMPlatform)
   .crossType(CrossType.Pure)
-  .in(file("."))
+  .in(file("collection-contrib"))
   .settings(ScalaModulePlugin.scalaModuleSettings)
   .jvmSettings(ScalaModulePlugin.scalaModuleSettingsJVM)
   .settings(