Update readme: v1.3.0 is released

Author: vlsi

README.md

@@ -7,15 +7,20 @@ CompactHashMap
 Usage
 -----
 
-Add maven dependency:
+Add Maven dependency:
 ```xml
 <dependency>
     <groupId>com.github.vlsi.compactmap</groupId>
     <artifactId>compactmap</artifactId>
-    <version>1.2.1</version>
+    <version>1.3.0</version>
 </dependency>
 ```
 
+Gradle:
+```kotlin
+compile("com.github.vlsi.compactmap:compactmap:1.3.0")
+```
+
 About
 -----
 This is a memory efficient alternative to HashMap.
@@ -82,7 +87,7 @@ or (at your option) any later version.
 
 Change log
 ----------
-HEAD
+v1.3.0
 * Improvement: implement null keys
 * Improvement: `Map#toString`
 * Improvement: `Map#hashCode` + `equals`