Drop Scala 2.11 support

.travis.yml

@@ -28,7 +28,7 @@ jobs:
     - stage: whitesource-release
       script: git branch -f "$TRAVIS_BRANCH" && git checkout "$TRAVIS_BRANCH" && sbt whitesourceCheckPolicies whitesourceUpdate
     - stage: publish
-      script: sbt "; ++2.11.12 publish ; ++2.12.8 publish"
+      script: sbt publish
     - script: openssl aes-256-cbc -K $encrypted_9c9c33071881_key -iv $encrypted_9c9c33071881_iv -in gradle.properties.enc -out ./gradle-plugin/gradle.properties -d && cd gradle-plugin && ./gradlew publishPlugins
     - stage: techhub-ping
       script: curl -I https://ci.lightbend.com/job/techhub-publisher/build?token=$TECH_HUB_TOKEN

CONTRIBUTING.md

@@ -101,7 +101,7 @@ rules:
 Binary compatibility rules and guarantees are described in depth in the [Binary Compatibility Rules
 ](http://doc.akka.io/docs/akka/snapshot/common/binary-compatibility-rules.html) section of the documentation.
 
-Akka-http uses MiMa (which is short for [Lightbend Migration Manager](https://github.com/lightbend/migration-manager)) to
+Akka HTTP uses MiMa (which is short for [Lightbend Migration Manager](https://github.com/lightbend/migration-manager)) to
 validate binary compatibility of incoming Pull Requests. If your PR fails due to binary compatibility issues, you may see 
 an error like this:
 

build.sbt

@@ -1,5 +1,5 @@
 import akka.grpc.Dependencies
-import akka.grpc.Dependencies.Versions.{ scala211, scala212 }
+import akka.grpc.Dependencies.Versions.scala212
 import akka.grpc.ProjectExtensions._
 import akka.grpc.build.ReflectiveCodeGen
 
@@ -53,9 +53,6 @@ lazy val runtime = Project(
   )
   .settings(Dependencies.runtime)
   .settings(commonSettings)
-  .settings(
-    crossScalaVersions := Seq(scala211, scala212)
-  )
 
 /** This could be an independent project - or does upstream provide this already? didn't find it.. */
 lazy val scalapbProtocPlugin = Project(
@@ -108,12 +105,6 @@ lazy val sbtPlugin = Project(
     scriptedDependencies := {
       val p1 = publishLocal.value
       val p2 = (publishLocal in codegen).value
-
-      // publish runtime for Scala 2.11 as well as some scripted tests use that 
-      val extracted = Project.extract(state.value)
-      val differentScalaVersion = extracted.appendWithSession(List(scalaVersion in runtime := scala211), state.value)
-      extracted.runTask(publishLocal in runtime, differentScalaVersion)
-
       val p3 = (publishLocal in runtime).value
       val p4 = (publishLocal in interopTests).value
     },

project/Dependencies.scala

@@ -6,7 +6,6 @@ import sbt.Keys._
 object Dependencies {
 
   object Versions {
-    val scala211 = "2.11.12"
     val scala212 = "2.12.8"
 
     val akka = "2.5.20"