NOJIRA: fix 'duplicate class error' during mvn test

Fix bug during mvn test phase (since PR #50)
 
[ERROR] COMPILATION ERROR : 
[INFO] -------------------------------------------------------------
[ERROR] /tmp/email-preview/src/test/java/org/jasig/portlet/emailpreview/util/MessageUtilsTest.java:[14,7] duplicate class: org.jasig.portlet.emailpreview.util.MessageUtilsTest