Add runtime dependency info for CassandraAppender
<td>NoSQL Appender with Apache CouchDB provider</td>
<td>LightCouch CouchDB client library</td>
</tr>
+ <tr>
+ <td>Cassandra Appender</td>
+ <td>Datastax Cassandra driver and Log4j NoSQL library</td>
+ </tr>
<tr>
<td>Bzip2, Deflate, Pack200, and XZ compression on rollover</td>
<td><a href="http://commons.apache.org/proper/commons-compress/">Apache Commons Compress</a>.
