<build>
  <plugins>
    ...
    <plugin>
      <groupId>org.apache.tomcat.maven</groupId>
      <artifactId>tomcat7-maven-plugin</artifactId>
      <version>2.2</version>
      <configuration>
        <path>/</path>
        <contextReloadable>true</contextReloadable>
      </configuration>
    </plugin>
    ...
  </plugins>
</build>