bump baseline Rakudo in travis CI

dwarring · dwarring · commit 419b75476852 · 2020-11-27T14:57:17.000+13:00
fixes failing deps
diff --git a/.travis.yml b/.travis.yml
@@ -2,7 +2,7 @@ language: perl6
 sudo: false
 perl6:
   - latest
-  - '2017.07'
+  - '2018.08'
 install:
   - rakudobrew build zef
   - zef --depsonly install .
