Revert MongoId::isValid() and use L5.1

composer.json

@@ -1,6 +1,6 @@
 {
     "name": "jenssegers/mongodb",
-    "description": "A MongoDB based Eloquent model and Query builder for Laravel 4",
+    "description": "A MongoDB based Eloquent model and Query builder for Laravel",
     "keywords": ["laravel","eloquent","mongodb","mongo","database","model"],
     "homepage": "https://github.com/jenssegers/laravel-mongodb",
     "authors": [
@@ -11,14 +11,14 @@
     ],
     "license" : "MIT",
     "require": {
-        "illuminate/support": "^5.1",
-        "illuminate/container": "^5.1",
-        "illuminate/database": "^5.1",
-        "illuminate/events": "^5.1"
+        "illuminate/support": "~5.1.0",
+        "illuminate/container": "~5.1.0",
+        "illuminate/database": "~5.1.0",
+        "illuminate/events": "~5.1.0"
     },
     "require-dev": {
         "phpunit/phpunit": "^4.0|^5.0",
-        "orchestra/testbench": "^3.1",
+        "orchestra/testbench": "~3.1.0",
         "mockery/mockery": "^0.9",
         "satooshi/php-coveralls": "^0.6"
     },

src/Jenssegers/Mongodb/Query/Builder.php

@@ -790,7 +790,7 @@ protected function performUpdate($query, array $options = [])
      */
     public function convertKey($id)
     {
-        if (MongoId::isValid($id))
+        if (is_string($id) and strlen($id) === 24 and ctype_xdigit($id))
         {
             return new MongoId($id);
         }