Add scala native to build matrix

Author: Philippus

Diff for: .travis.yml

@@ -22,6 +22,10 @@ env:
     - SCALAJS_VERSION=0.6.27
     - SCALAJS_VERSION=1.0.0-M7
 
+    include:
+      - env: SCALANATIVE_VERSION=0.3.8
+        jdk: oraclejdk8
+
 script: admin/build.sh
 
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