Update Jacoco version

May fix an issue with code coverage instrumentation; Jacoco fails with a stack overflow, presumably because it is scanning its own files.
diff --git a/pom.xml b/pom.xml
index 3e11d43..dabd4dc 100644
--- a/pom.xml
+++ b/pom.xml
@@ -71,7 +71,7 @@
       <plugin>
         <groupId>org.jacoco</groupId>
         <artifactId>jacoco-maven-plugin</artifactId>
-        <version>0.7.4.201502262128</version>
+        <version>0.7.7.201606060606</version>
         <executions>
           <execution>
             <id>pre-unit-test</id>