Add dis max query doc.

docs/Query/DisMax.md

+# Dis Max query
+
+> More info about Dis Max query is in the [official elasticsearch docs][1]
+
+A query that generates the union of documents produced by its subqueries, and that scores each document with the
+maximum score for that document as produced by any subquery, plus a tie breaking increment for any additional matching
+subqueries.
+
+Lets try to write this example
+```JSON
+{
+    "dis_max" : {
+        "tie_breaker" : 0.7,
+        "boost" : 1.2,
+        "queries" : [
+            {
+                "term" : { "age" : 34 }
+            },
+            {
+                "term" : { "age" : 35 }
+            }
+        ]
+    }
+}
+```
+
+In DSL :
+
+```php
+$term1 = new TermQuery('age', 34);
+$term2 = new TermQuery('age', 35);
+
+$disMax = new DisMaxQuery();
+$disMax->addParameter('tie_breaker', 0.7);
+$disMax->addParameter('boost', 1.2);
+$disMax->addQuery($term1);
+$disMax->addQuery($term2);
+
+$search = new Search();
+$search->addQuery($disMax);
+
+$queryArray = $search->toArray();
+```
+
+[1]: https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-dis-max-query.html