CASSJAVA-81 Added license and Maven Central badges, fix typo

patch by Brad Schoening; reviewed by Andrew Tolbert for CASSJAVA-81

Author: bschoening

README.md

@@ -2,6 +2,9 @@
 
 :warning: The java-driver has recently been donated by Datastax to The Apache Software Foundation and the Apache Cassandra project.  Bear with us as we move assets and coordinates.
 
+[![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://opensource.org/licenses/Apache-2.0)
+[![Maven Central](https://maven-badges.herokuapp.com/maven-central/org.apache.cassandra/cassandra-driver-core/badge.svg)](https://maven-badges.herokuapp.com/maven-central/org.apache.cassandra/cassandra-driver-core)
+
 *If you're reading this on github.com, please note that this is the readme
 for the development version and that some features described here might
 not yet have been released. You can find the documentation for the latest
@@ -82,7 +85,7 @@ The 'extras' module is also published as a separate artifact:
 <dependency>
   <groupId>org.apache.cassandra</groupId>
   <artifactId>cassandra-driver-extras</artifactId>
-  <version>3.12.1/version>
+  <version>3.12.1</version>
 </dependency>
 ```