FIX Prefer source for framework so we can run tests for it

.travis.yml

@@ -32,6 +32,7 @@ before_script:
   - composer validate
   - composer require --no-update silverstripe/recipe-cms:2.x-dev
   - composer install --prefer-dist --no-interaction --no-progress --no-suggest --optimize-autoloader --verbose --profile
+  - composer require --prefer-source silverstripe/framework 5.x-dev
   - if [[ $PHPCS_TEST ]]; then composer global require squizlabs/php_codesniffer:^3 --prefer-dist --no-interaction --no-progress --no-suggest -o; fi
 
 script: