Add closing p tag

After discussion with sharell it turns out that some of the automated
 translation tools used for creating other ANTLR language targets look 
for closing tags (for one reason or another), so for this project 
the practice is to explicitly close all tags.

antlr4-maven-plugin/src/main/java/org/antlr/mojo/antlr4/Antlr4ErrorLog.java

@@ -65,7 +65,7 @@ public class Antlr4ErrorLog implements ANTLRToolListener {
      * {@inheritDoc}
      * <p>
      * This implementation passes the message to the Maven log.
-     *
+     * </p>
      * @param message The message to send to Maven
      */
     @Override
@@ -80,7 +80,7 @@ public class Antlr4ErrorLog implements ANTLRToolListener {
      * {@inheritDoc}
      * <p>
      * This implementation passes the message to the Maven log.
-     *
+     * </p>
      * @param message The message to send to Maven.
      */
     @Override
@@ -103,7 +103,7 @@ public class Antlr4ErrorLog implements ANTLRToolListener {
      * {@inheritDoc}
      * <p>
      * This implementation passes the message to the Maven log.
-     *
+     * </p>
      * @param message
      */
     @Override

antlr4-maven-plugin/src/main/java/org/antlr/mojo/antlr4/Antlr4Mojo.java

@@ -150,6 +150,7 @@ public class Antlr4Mojo extends AbstractMojo {
 	 * A set of Ant-like inclusion patterns used to select files from the source
 	 * directory for processing. By default, the pattern
 	 * <code>**&#47;*.g4</code> is used to select grammar files.
+	 * </p>
 	 */
     @Parameter
     protected Set<String> includes = new HashSet<String>();