Fix for zip codes with leading zeros (#4)

* Fix for zip codes with leading zeros

* Update postal code doc type

* Change zipcode type to string

Author: MichaelMackus

src/Lookup.php

@@ -5,7 +5,7 @@
 
 class Lookup
 {
-    const ZIPTASTIC_LOOKUP_URL = 'https://zip.getziptastic.com/v3/%s/%d';
+    const ZIPTASTIC_LOOKUP_URL = 'https://zip.getziptastic.com/v3/%s/%s';
 
     /**
      * @var ServiceInterface;
@@ -42,12 +42,12 @@ public static function create($apiKey = null, $countryCode = 'US')
 
     /**
      * Get information on given $zipCode
-     * @param  int                $zipCode
+     * @param  string           $zipCode
      * @return array[LookupModel]
      */
     public function lookup($zipCode)
     {
-        $url = sprintf(self::ZIPTASTIC_LOOKUP_URL, $this->countryCode, $zipCode);
+        $url = sprintf(self::ZIPTASTIC_LOOKUP_URL, $this->countryCode, (string) $zipCode);
         $res = $this->service->get($url, $this->apiKey);
 
         $collection = [];
@@ -57,4 +57,4 @@ public function lookup($zipCode)
 
         return $collection;
     }
-}
+}

src/LookupModel.php

@@ -25,7 +25,7 @@ class LookupModel
     private $stateShort;
 
     /**
-     * @var int
+     * @var string
      */
     private $postalCode;
 
@@ -95,7 +95,7 @@ public function stateShort()
     }
 
     /**
-     * @return int
+     * @return string
      */
     public function postalCode()
     {