[maven-release-plugin] prepare for next development iteration

pom.xml

@@ -10,7 +10,7 @@
 
     <groupId>ch.fritteli.a-maze-r</groupId>
     <artifactId>maze-generator</artifactId>
-    <version>0.5.0</version>
+    <version>0.5.1-SNAPSHOT</version>
 
     <name>A-Maze-R Generator</name>
     <description>A-Maze-R, The Maze Generator. It is a library for generating mazes in various output formats.
@@ -44,7 +44,7 @@
         <connection>scm:git:https://gittr.ch/java/maze-generator.git</connection>
         <developerConnection>scm:git:ssh://git@gittr.ch/java/maze-generator.git</developerConnection>
         <url>https://gittr.ch/java/maze-generator</url>
-        <tag>v0.5.0</tag>
+        <tag>HEAD</tag>
     </scm>
 
     <distributionManagement>