Use Travis CI minimal environment

PeterDaveHello · PeterDaveHello · commit 21c29597aab7 · 2018-11-14T20:29:44.000+08:00
diff --git a/.travis.yml b/.travis.yml
@@ -1,4 +1,4 @@
-language: generic
+language: minimal
 dist: xenial
 
 git:
