Eliminates ruby from the build

It's just eight seconds, but it's not really needed. This goes towards
solving #2498.

Author: JJ

.travis.yml

@@ -1,5 +1,8 @@
+language:
+  - minimal
+  
 os:
-    - linux
+  - linux
 
 cache:
     directories:
@@ -8,6 +11,8 @@ cache:
         - highlights/node_modules
         - $HOME/.rakudobrew
 
+
+
 services:
   - docker