Remove bintray, provide maven central link (#13)

Author: kleewho

README.md

@@ -3,8 +3,7 @@
 [![Build Status](https://travis-ci.com/pubnub/kotlin.svg?branch=master)](https://travis-ci.com/pubnub/kotlin)
 [![Codacy Badge](https://api.codacy.com/project/badge/Grade/164fd518c314417e896b3de494ab75df)](https://www.codacy.com/app/PubNub/kotlin?utm_source=github.com&utm_medium=referral&utm_content=pubnub/kotlin&utm_campaign=Badge_Grade)
 [![Codacy Badge](https://api.codacy.com/project/badge/Coverage/164fd518c314417e896b3de494ab75df)](https://www.codacy.com/app/PubNub/kotlin?utm_source=github.com&utm_medium=referral&utm_content=pubnub/kotlin&utm_campaign=Badge_Coverage)
-[![Download](https://api.bintray.com/packages/bintray/jcenter/com.pubnub%3Apubnub-kotlin/images/download.svg)](https://bintray.com/bintray/jcenter/com.pubnub%3Apubnub-kotlin/_latestVersion)
-[![Maven Central](https://img.shields.io/maven-central/v/com.pubnub/pubnub-kotlin.svg)]()
+[![Maven Central](https://img.shields.io/maven-central/v/com.pubnub/pubnub-kotlin.svg)](https://maven-badges.herokuapp.com/maven-central/com.pubnub/pubnub-kotlin)
 
 This is the official PubNub Kotlin SDK repository.