Remove Scala 2.11 compat code

Author: ddworak

core/src/test/scala/com/avsystem/commons/serialization/CodecTestData.scala

@@ -80,16 +80,14 @@ object CodecTestData {
     @mongoId def id: String
     @generated @name("upper_id") def upperId: String = id.toUpperCase
   }
-  object FlatSealedBase {
+  object FlatSealedBase extends HasGenCodec[FlatSealedBase] {
     case class FirstCase(id: String, int: Int = 42) extends FlatSealedBase
     case class SecondCase(id: String, dbl: Double, moar: Double*) extends FlatSealedBase
     case object ThirdCase extends FlatSealedBase {
       @generated def id = "third"
     }
     case class RecursiveCase(id: String, sub: Opt[FlatSealedBase]) extends FlatSealedBase
     case class LocallyRecursiveCase(id: String, sub: Opt[LocallyRecursiveCase]) extends FlatSealedBase
-    // for Scala 2.11
-    implicit val codec: GenCodec[FlatSealedBase] = GenCodec.materialize
   }
 
   @flatten sealed trait TransparentFlatSealedBase

mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/MongoRef.scala

@@ -9,6 +9,7 @@ import com.avsystem.commons.mongo.{BsonValueInput, KeyEscaper}
 import com.avsystem.commons.serialization.GenCodec.ReadFailure
 import com.avsystem.commons.serialization.TransparentWrapping
 import org.bson.{BsonDocument, BsonValue}
+import scala.annotation.tailrec
 
 /**
   * Represents a reference to a particular "place" in a MongoDB document. The "place" may be an actual path
@@ -188,9 +189,7 @@ sealed trait MongoPropertyRef[E, T] extends MongoRef[E, T]
   def twoDimIndex: MongoIndex[E] = index(MongoIndexType.TwoDim)
   def twoDimSphereIndex: MongoIndex[E] = index(MongoIndexType.TwoDimSphere)
 
-  //noinspection NoTailRecursionAnnotation
-  //no @tailrec because Scala 2.11 has problems with it
-  private def computePath[T0](
+  @tailrec private def computePath[T0](
     onlyUpToArray: Boolean,
     ref: MongoPropertyRef[E, T0],
     acc: List[String],