Prepare release 1.4.0 (#33)

Author: marchof

README.md

@@ -23,7 +23,7 @@ The latest Three4J version can be obtained with the following Maven dependency:
 <dependency>
     <groupId>com.mountainminds</groupId>
     <artifactId>three4j</artifactId>
-    <version>1.3.0</version>
+    <version>1.4.0</version>
 </dependency>
 ```
 

pom.xml

@@ -4,7 +4,7 @@
 	<modelVersion>4.0.0</modelVersion>
 	<groupId>com.mountainminds</groupId>
 	<artifactId>three4j</artifactId>
-	<version>1.3.1-SNAPSHOT</version>
+	<version>1.4.0</version>
 
 	<name>Three4J - Threema Client API for Java</name>
 	<description>Client API for Threema Messanger</description>