[CI] use trusty to get phantomjs 2.0.0+

Otherwise we get error Can't find variable: MutationObserver
8 years ago · 9298c999b9
1 changed files with 1 additions and 0 deletions
--- a/.travis.yml
+++ b/.travis.yml
@ -3,6 +3,7 @@ language: python
 python:
  - "2.7"
  
+dist: trusty
 sudo: false
 cache: pip