Fix Markdown syntax for Travis build status image

MidnightLightning · davidlehn · commit 1f96ec8691c0 · 2019-05-17T14:19:24.000-04:00
diff --git a/README.md b/README.md
@@ -2,6 +2,7 @@ php-json-ld
 ===========
 
 [![Build Status][travis-ci-png]][travis-ci-site]
+
 [travis-ci-png]: https://travis-ci.org/digitalbazaar/php-json-ld.png?branch=master
 [travis-ci-site]: https://travis-ci.org/digitalbazaar/php-json-ld
 
