Run update instead of install to update the lock file

.gitignore

@@ -1,4 +1,4 @@
 .DS_Store
 .idea/
-vendor/*
+vendor/
 tests/.env

.travis.yml

@@ -74,7 +74,7 @@ script:
   - drush trp-run-jobs --username=admin
 
   # Run PHPUnit tests
-  - composer install
+  - composer update
   - ./vendor/bin/phpunit
 
   # Test Tripal v2 to v3 upgrade steps

composer.json

@@ -1,5 +1,6 @@
 {
   "require-dev": {
+    "doctrine/instantiator": "1.0.*",
     "statonlab/tripal-test-suite": "~1.0.0"
   }
 }