MAGETWO-72344: Enhancement: Configure preferred installation source in composer.json #10774

 - Merge Pull Request #10774 from localheinz/magento2:feature/preferred-install
 - Merged commits:
   1. bfe8135

Author: orlangur

.travis.yml

@@ -48,7 +48,7 @@ cache:
     - $HOME/node_modules
     - $HOME/yarn.lock
 before_install: ./dev/travis/before_install.sh
-install: composer install --no-interaction --prefer-dist
+install: composer install --no-interaction
 before_script: ./dev/travis/before_script.sh
 script:
   # Set arguments for variants of phpunit based tests; '|| true' prevents failing script when leading test fails

composer.json

@@ -7,6 +7,9 @@
         "OSL-3.0",
         "AFL-3.0"
     ],
+    "config": {
+        "preferred-install": "dist"
+    },
     "require": {
         "php": "7.0.2|7.0.4|~7.0.6|~7.1.0",
         "zendframework/zend-stdlib": "^2.7.7",