enable apt caching on travis

aminroosta · aminroosta · commit ed82cb3aa76d · 2018-02-03T17:02:06.000+08:00
diff --git a/.travis.yml b/.travis.yml
@@ -3,6 +3,7 @@ sudo: required
 dist: trusty
 
 cache:
+  apt: true
   directories:
     - /home/travis/.hunter/
 
