Add tojson method

Fixes #101

CHANGELOG.md

@@ -2,6 +2,10 @@
 All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
+## [4.0.21] - 3 Nov 2018
+### Added
+- `->toJson()` method when querying results.
+
 ## [4.0.10] - 1 Jul 2018
 ### Changed
 - service provider to register singleton and alias in `register()` method.

src/ProviderAndDumperAggregator.php

@@ -51,6 +51,13 @@ public function get() : Collection
         return $this->results;
     }
 
+    public function toJson() : string
+    {
+        return $this
+            ->dump("geojson")
+            ->first();
+    }
+
     public function dump(string $dumper) : Collection
     {
         $dumperClasses = collect([