Moved jacoco version to variable

pom.xml

@@ -31,6 +31,7 @@
         <compiler.plugin>3.3</compiler.plugin>
         <source.plugin>2.4</source.plugin>
         <shade.plugin>2.4.3</shade.plugin>
+        <jacoco.plugin>0.8.1</jacoco.plugin>
 
         <!-- Classifiers -->
         <grammars.classifier>grammars</grammars.classifier>
@@ -172,7 +173,7 @@
             <plugin>
                 <groupId>org.jacoco</groupId>
                 <artifactId>jacoco-maven-plugin</artifactId>
-                <version>0.7.5.201505241946</version>
+                <version>${jacoco.plugin}</version>
                 <executions>
                     <execution>
                         <id>pre-unit-test</id>