fix(ci): fix travis references

Author: benjie

scripts/ci

@@ -15,7 +15,7 @@ echo "Undoing changes to autogenerated files"
 git checkout -- src/data/examples.json
 git checkout -- src/pages/postgraphile/usage-*.md
 
-if [ "$GITHUB_TOKEN" != "" ] && [ "$TRAVIS_PULL_REQUEST" == "false" ] && [ "$TRAVIS_BRANCH" == "develop" ]; then
+if [ "$GITHUB_TOKEN" != "" ] && [ "$GITHUB_BASE_REF" != "" ] && [ "$GITHUB_REF" == "ref/heads/develop" ]; then
   echo "GITHUB_TOKEN is specified"
 
   # git diff-index only looks at modified timestamps; this update-index call