Using better composer flags to speed up travis (#132)

* Using better composer flags to speed up travis

* Prefer dist and stable

Author: Nyholm

.travis.yml

@@ -13,7 +13,7 @@ cache:
       - "$HOME/.composer/cache"
 
 install:
-    - composer update
+    - composer update --prefer-dist --prefer-stable
 
 script:
     - ./vendor/bin/phpunit --coverage-clover=coverage.xml