Build Scala.js 1.0 for Scala 2.11 and 2.13

Author: ashawley

Diff for: .travis.yml

@@ -31,8 +31,8 @@ env:
 
 matrix:
   exclude:
-    - scala: 2.13.0-M3
-      env: SCALAJS_VERSION=1.0.0-M3
+    - jdk: oraclejdk9
+      env: SCALAJS_VERSION=0.6.23
     - jdk: oraclejdk9
       env: SCALAJS_VERSION=1.0.0-M3
     - scala: 2.11.12