chore(release): prepare for next development iteration

pom.xml

@@ -2,7 +2,7 @@
   <modelVersion>4.0.0</modelVersion>
   <groupId>io.socket</groupId>
   <artifactId>socket.io-client</artifactId>
-  <version>2.1.2</version>
+  <version>2.1.3-SNAPSHOT</version>
   <packaging>jar</packaging>
   <name>socket.io-client</name>
   <description>Socket.IO Client Library for Java</description>
@@ -30,7 +30,7 @@
     <url>https://github.com/socketio/socket.io-client-java</url>
     <connection>scm:git:https://github.com/socketio/socket.io-client-java.git</connection>
     <developerConnection>scm:git:https://github.com/socketio/socket.io-client-java.git</developerConnection>
-    <tag>socket.io-client-2.1.2</tag>
+    <tag>HEAD</tag>
   </scm>
 
   <developers>
@@ -184,7 +184,7 @@
       <plugin>
         <groupId>org.sonatype.plugins</groupId>
         <artifactId>nexus-staging-maven-plugin</artifactId>
-        <version>1.6.7</version>
+        <version>1.6.13</version>
         <extensions>true</extensions>
         <configuration>
           <serverId>ossrh</serverId>