Update java version to 1.7 - see #252

Author: aleksandr-m

pom.xml

@@ -63,7 +63,7 @@
     </distributionManagement>
 
     <properties>
-        <java.version>1.6</java.version>
+        <java.version>1.7</java.version>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <scm.url>scm:git:[email protected]:aleksandr-m/gitflow-maven-plugin.git</scm.url>
         <url>https://github.com/aleksandr-m/gitflow-maven-plugin</url>