Update to more recent compiler plugin.

Also bumped source/target to 1.6. Hopefully this won't result in backlash from
cavemen still using JMustache on JDK 1.5.

pom.xml

@@ -83,15 +83,18 @@
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-compiler-plugin</artifactId>
-        <version>2.3.2</version>
+        <version>3.1</version>
         <configuration>
-          <source>1.5</source>
-          <target>1.5</target>
+          <source>1.6</source>
+          <target>1.6</target>
           <fork>true</fork>
           <showDeprecation>true</showDeprecation>
           <showWarnings>true</showWarnings>
-          <!-- yes, those quoted spaces are a workaround sanctioned by the Maven idiocracy -->
-          <compilerArgument>-Xlint" "-Xlint:-serial" "-Xlint:-path</compilerArgument>
+          <compilerArgs>
+            <arg>-Xlint</arg>
+            <arg>-Xlint:-serial</arg>
+            <arg>-Xlint:-path</arg>
+          </compilerArgs>
           <excludes>
             <exclude>com/samskivert/gwt/**</exclude>
           </excludes>
@@ -170,7 +173,7 @@
         <version>2.5</version>
       </plugin>
 
-<!-- these handle code coverage -->
+      <!-- these handle code coverage -->
       <plugin>
         <groupId>org.codehaus.mojo</groupId>
         <artifactId>cobertura-maven-plugin</artifactId>