Add Travis badge

Author: rdunklau

Diff for: README.md

@@ -1,4 +1,5 @@
-[![PGXN version](https://badge.fury.io/pg/multicorn.svg)](https://badge.fury.io/pg/multicorn) [![Build Status](https://jenkins.dalibo.info/buildStatus/public/Multicorn)]()
+[![PGXN version](https://badge.fury.io/pg/multicorn.svg)](https://badge.fury.io/pg/multicorn)
+[![Build Status](https://travis-ci.org/Segfault-Inc/Multicorn.svg?branch=master)](https://travis-ci.org/Segfault-Inc/Multicorn)
 
 Multicorn
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