[ci] oraclejdk7 and openjdk6 builds fail on Trusty. Switching back to Precise for now.

harawata · harawata · commit 5f787f11a9cd · 2017-08-13T14:09:17.000+09:00
travis-ci/travis-ci#7884 https://travis-ci.org/mybatis/mybatis-3/builds/263982308
diff --git a/.travis.yml b/.travis.yml
@@ -1,5 +1,6 @@
 language: java
 sudo: false
+dist: precise
 
 jdk:
   - oraclejdk8
