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

pom.xml

@@ -3,7 +3,7 @@
     <groupId>de.jollyday</groupId>
     <artifactId>jollyday</artifactId>
     <name>Jollyday</name>
-    <version>0.5.5</version>
+    <version>0.5.6-SNAPSHOT</version>
     <description>
         This API determines the holidays for a given year, country/name and eventually state/region. The holiday data is
         stored in XML files (one for each country) and will be read from the classpath. You can provide your own holiday
@@ -87,7 +87,7 @@
         <connection>scm:git:git://github.com/svendiedrichsen/jollyday.git</connection>
         <developerConnection>scm:git:git@github.com:svendiedrichsen/jollyday.git</developerConnection>
         <url>https://github.com/svendiedrichsen/jollyday.git</url>
-        <tag>v_0_5_5</tag>
+        <tag>HEAD</tag>
     </scm>
     <build>
         <pluginManagement>