add jdk11 test

Author: xuwei-k

.travis.yml

@@ -7,6 +7,11 @@ scala:
 jdk:
   - oraclejdk8
 
+matrix:
+  include:
+  - jdk: oraclejdk11
+    scala: 2.12.7
+
 sudo: required
 dist: trusty
 

core/jvm/src/main/scala/fs2/compress.scala

@@ -38,7 +38,7 @@ object compress {
           _deflate_collect(deflater, buffer, ArrayBuffer.empty, false).toArray
         Pull.output(Chunk.bytes(result)) >> _deflate_stream(deflater, buffer)(tl)
       case None =>
-        deflater.setInput(Array.empty)
+        deflater.setInput(Array.empty[Byte])
         deflater.finish()
         val result =
           _deflate_collect(deflater, buffer, ArrayBuffer.empty, true).toArray