Fix missing ]

Author: pakoito

README.md

@@ -2,7 +2,7 @@
 
 [![Maven Central](https://maven-badges.herokuapp.com/maven-central/io.arrow-kt/arrow-core/badge.svg)](https://maven-badges.herokuapp.com/maven-central/io.arrow-kt/arrow-core)
 [![Build Status](https://travis-ci.org/arrow-kt/arrow.svg?branch=master)](https://travis-ci.org/arrow-kt/arrow/)
-[![Kotlin version badge](https://img.shields.io/badge/kotlin-1.3-blue.svg)
+[![Kotlin version badge]](https://img.shields.io/badge/kotlin-1.3-blue.svg)
 [![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](http://www.apache.org/licenses/LICENSE-2.0)
 [![codecov](https://codecov.io/gh/arrow-kt/arrow/branch/master/graph/badge.svg)](https://codecov.io/gh/arrow-kt/arrow)