Added count method

Author: babenkoivan

README.md

@@ -207,7 +207,14 @@ App\MyModel::search('phone')
     ->get();
 ```
 
-If you need to load relations you can use the `with` method:
+If you only need the number of matches for a query, use the `count` method:
+
+```php
+App\MyModel::search('phone') 
+    ->count();
+```
+
+If you need to load relations, use the `with` method:
 
 ```php
 App\MyModel::search('phone') 

src/Builders/FilterBuilder.php

@@ -270,4 +270,14 @@ public function select($fields)
 
         return $this;
     }
+
+    /**
+     * @return int
+     */
+    public function count()
+    {
+        return $this
+            ->engine()
+            ->count($this);
+    }
 }

src/ElasticEngine.php

@@ -180,6 +180,29 @@ public function profile(Builder $builder)
         ]);
     }
 
+    /**
+     * @param Builder $builder
+     * @return int
+     */
+    public function count(Builder $builder)
+    {
+        $count = 0;
+
+        $this
+            ->buildSearchQueryPayloadCollection($builder)
+            ->each(function($payload) use (&$count) {
+                $result = ElasticClient::count($payload);
+
+                $count = $result['count'];
+
+                if ($count > 0) {
+                    return false;
+                }
+        });
+
+        return $count;
+    }
+
     public function searchRaw(Model $model, $query)
     {
         $payload = (new TypePayload($model))

tests/ElasticEngineTest.php

@@ -201,6 +201,48 @@ public function testBuildFilterQueryPayloadCollection()
         );
     }
 
+    public function testCount()
+    {
+        ElasticClient
+            ::shouldReceive('count')
+            ->once()
+            ->with([
+                'index' => 'test',
+                'type' => 'test',
+                'body' => [
+                    'query' => [
+                        'bool' => [
+                            'must' => [
+                                'match_all' => new stdClass()
+                            ],
+                            'filter' => [
+                                'bool' => [
+                                    'must' => [
+                                        [
+                                            'term' => [
+                                                'foo' => 'bar'
+                                            ]
+                                        ]
+                                    ]
+                                ]
+                            ]
+                        ]
+                    ]
+                ]
+            ]);
+
+        $model = $this->mockModel();
+
+        $filterBuilder = (new FilterBuilder($model))
+            ->where('foo', 'bar');
+
+        $this
+            ->engine
+            ->count($filterBuilder);
+
+        $this->addToAssertionCount(1);
+    }
+
     public function testSearchRaw()
     {
         ElasticClient