Add sbt support for retrofit.

modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/JavaClientCodegen.java

@@ -332,6 +332,8 @@ public class JavaClientCodegen extends DefaultCodegen implements CodegenConfig {
                     gradleWrapperPackage.replace( ".", File.separator ), "gradle-wrapper.properties") ); 
             supportingFiles.add( new SupportingFile( "gradle-wrapper.jar", 
                     gradleWrapperPackage.replace( ".", File.separator ), "gradle-wrapper.jar") );
+            // "build.sbt" is for development with SBT
+            supportingFiles.add(new SupportingFile("build.sbt.mustache", "", "build.sbt"));
 
             //generate markdown docs for retrofit2
             if ( usesRetrofit2Library() ){

modules/swagger-codegen/src/main/resources/Java/libraries/retrofit/build.sbt.mustache

@@ -0,0 +1,19 @@
+lazy val root = (project in file(".")).
+  settings(
+    organization := "{{groupId}}",
+    name := "{{artifactId}}",
+    version := "{{artifactVersion}}",
+    scalaVersion := "2.11.4",
+    scalacOptions ++= Seq("-feature"),
+    javacOptions in compile ++= Seq("-Xlint:deprecation"),
+    publishArtifact in (Compile, packageDoc) := false,
+    resolvers += Resolver.mavenLocal,
+    libraryDependencies ++= Seq(
+      "com.squareup.okhttp" % "okhttp" % "2.7.5" % "compile",
+      "com.squareup.retrofit" % "retrofit" % "1.9.0" % "compile",
+      "io.swagger" % "swagger-annotations" % "1.5.8" % "compile",
+      "org.apache.oltu.oauth2" % "org.apache.oltu.oauth2.client" % "1.0.1" % "compile",
+      "junit" % "junit" % "4.12" % "test",
+      "com.novocode" % "junit-interface" % "0.10" % "test"
+    )
+  )