Add --fail to curl snippet. (#27)

Author: artem-zinnatullin

README.md

@@ -89,7 +89,7 @@ Composer is [available on jcenter](https://jcenter.bintray.com/com/gojuno/compos
 
 ```console
 COMPOSER_VERSION=some-version
-curl --location https://jcenter.bintray.com/com/gojuno/composer/composer/${COMPOSER_VERSION}/composer-${COMPOSER_VERSION}.jar --output /tmp/composer.jar
+curl --fail --location https://jcenter.bintray.com/com/gojuno/composer/composer/${COMPOSER_VERSION}/composer-${COMPOSER_VERSION}.jar --output /tmp/composer.jar
 ```
 
 All the releases and changelogs can be found on [Releases Page](https://github.com/gojuno/composer/releases).