Added support for validating token issuer and audience

* Use requireIssuer() and requireAudience() on the JwtValidator to make sure
  that the token is for what you expect it to be for.
* A setAll() method has been added to property bag, applying but not overriding
  values.
* Added tests for JwtValidator.

src/Collection/PropertyBag.php

@@ -45,6 +45,14 @@ class PropertyBag
         $this->props[$prop] = $value;
     }
 
+    public function setAll(array $props)
+    {
+        $this->props = array_merge(
+            $this->props,
+            $props
+        );
+    }
+
     /**
      * Get the value of a property, fails if the property does not exist.
      * Use the value() method to get with a default value
@@ -122,4 +130,4 @@ class PropertyBag
         return true;
     }
 
-}
+}