Add guild#createRole resolve permissions and RoleData optional (#1321)

* resolving permissions

* make RoleData optional

src/structures/Guild.js

@@ -683,7 +683,7 @@ class Guild {
    * .then(role => console.log(`Created role ${role}`))
    * .catch(console.error)
    */
-  createRole(data) {
+  createRole(data = {}) {
     return this.client.rest.methods.createGuildRole(this, data);
   }