Add entry for proguard optimized version in readme and changelog

Author: patrickfav

CHANGELOG

@@ -1,10 +1,12 @@
 # Releases
 
 ## v0.5.0
+
  * better resource handling for compression
  * add nullSafe from() constructor
  * rename `toObjectArray()` to `toBoxedArray()` (will be removed in 1.0)
  * add appendNullSafe and append string with encoding
+ * add proguard optimized version (can be used with classifier 'optimized')
 
 ## v0.4.6
 

README.md

@@ -53,6 +53,8 @@ Add dependency to your `pom.xml`:
         <version>{latest-version}</version>
     </dependency>
 
+_Note:_ There is a byte-code optimized version (powerd by [ProGuard](https://www.guardsquare.com/en/products/proguard)) which can be used with [classifier](https://maven.apache.org/pom.html#Maven_Coordinates) 'optimized'. This may have issues so use at your own risk.
+
 Some simple examples:
 
 ```java