Revert "Temporarily use the old Travis image."

kennytm · kennytm · commit 2352a888a19b · 2017-12-23T18:10:36.000+08:00
This reverts commit c0c26a6.
diff --git a/.travis.yml b/.travis.yml
@@ -1,7 +1,6 @@
 language: shell
 sudo: required
 dist: trusty
-group: deprecated-2017Q4
 services:
   - docker
 
