Set version to 2.8-SNAPSHOT

pom.xml

diff --git a/pom.xml b/pom.xml
index be957e2..6db3f29 100644
--- a/pom.xml
+++ b/pom.xml
@@ -23,7 +23,7 @@
   <name>commit-message-length-validator</name>
   <groupId>com.googlesource.gerrit.plugins.validators</groupId>
   <packaging>jar</packaging>
-  <version>2.7-SNAPSHOT</version>
+  <version>2.8-SNAPSHOT</version>
 
   <properties>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>