update

.travis.yml

 language: cpp
-dist: trusty
+dist: xenial
 git:
   submodules: false
 addons:
   ssh_known_hosts:
   - github.com
   apt:
-    sources:
-      - ubuntu-toolchain-r-test
     packages:
-      - gcc-6
-      - g++-6
       - libevent-dev
       - libsqlite3-dev
 env:
 - DATABASE_FILE=expansions/7cgl.cdb
 
 before_install:
-- sudo ln -s /usr/bin/gcc-6 /usr/local/bin/gcc
-- sudo ln -s /usr/bin/g++-6 /usr/local/bin/g++
 - git clone --depth=1 --branch=server --recursive https://github.com/purerosefallen/ygopro
 - cd ygopro