The build process throws errors

When you try to build the Elasticsearch app from the Rivet's repo (https://github.com/rivetlogic/liferay-elasticsearch-integration), it fails. It throws this error:
    [mkdir] Created dir: /Users/manuelcalvo/git/liferay-elasticsearch-integration/portlets/elasticsearch-portlet/docroot/WEB-INF/classes
     [copy] Copying 5 files to /Users/manuelcalvo/git/liferay-elasticsearch-integration/portlets/elasticsearch-portlet/docroot/WEB-INF/lib
compile-java:
     [copy] Copying 2 files to /Users/manuelcalvo/git/liferay-elasticsearch-integration/portlets/elasticsearch-portlet/docroot/WEB-INF/classes
     [copy] Copied 7 empty directories to 6 empty directories under /Users/manuelcalvo/git/liferay-elasticsearch-integration/portlets/elasticsearch-portlet/docroot/WEB-INF/classes
    [javac] Compiling 5 source files to /Users/manuelcalvo/git/liferay-elasticsearch-integration/portlets/elasticsearch-portlet/docroot/WEB-INF/classes
    [javac] ----------
    [javac] 1. ERROR in /Users/manuelcalvo/git/liferay-elasticsearch-integration/portlets/elasticsearch-portlet/docroot/WEB-INF/src/com/rivetlogic/elasticsearch/portlet/util/ElasticsearchPortletHelper.java (at line 29)
    [javac] import org.elasticsearch.action.search.SearchRequestBuilder;
    [javac] ^^^^^^^^^^^^^^^^^
    [javac] The import org.elasticsearch cannot be resolved
    [javac] ----------
    [javac] 2. ERROR in /Users/manuelcalvo/git/liferay-elasticsearch-integration/portlets/elasticsearch-portlet/docroot/WEB-INF/src/com/rivetlogic/elasticsearch/portlet/util/ElasticsearchPortletHelper.java (at line 30)
    [javac] import org.elasticsearch.action.search.SearchResponse;
    [javac] ^^^^^^^^^^^^^^^^^
    [javac] The import org.elasticsearch cannot be resolved