Fix SBT project references and dependency

SBT detects now client and server as independent projects with their own
names. Also, when compiling the server for the first time the client is
also compiled as a dependency.

.travis.yml

@@ -11,7 +11,7 @@ cache:
     - $HOME/.sbt/boot/
 script:
   - sbt test
-  - sbt scaladexJVM/universal:packageBin
+  - sbt server/universal:packageBin
   # - sbt sbtScaladex/scripted
 
 git:

README.MD

@@ -95,7 +95,7 @@ $ git submodule init
 $ git submodule update
 $ sbt
 > data/reStart elastic # do only once to populate the indices
-> project scaladexJVM # this is the server
+> project server
 > ~re-start
 ```
 

build.sbt

@@ -1,4 +1,5 @@
 import ScalaJSHelper._
+import org.scalajs.sbtplugin.cross.CrossProject
 
 lazy val baseSettings = Seq(
   organization := "ch.epfl.scala.index",
@@ -45,8 +46,8 @@ lazy val template = project
   .dependsOn(model)
   .enablePlugins(SbtTwirl)
 
-lazy val scaladex = crossProject.crossType(CustomCrossType)
-  .in(new File(".")) // use local dir to create "client" and "server" folders
+lazy val scaladex =
+  CrossProject("server", "client", new File("."), CustomCrossType)
   .settings(commonSettings: _*)
   .settings(
     libraryDependencies ++= Seq(
@@ -82,7 +83,7 @@ lazy val server = scaladex.jvm
       "-Xmx3g"
     )
   )
-  .dependsOn(template, data)
+  .dependsOn(client, template, data)
   .enablePlugins(SbtSass, JavaServerAppPackaging)
 
 lazy val model = project