Overload GoogleCredentials.createScoped with variadic arguments (#218)

* Add variadic overload of GoogleCredentials.createScoped * Remove unused import

Author: chingor13

oauth2_http/java/com/google/auth/oauth2/GoogleCredentials.java

@@ -227,6 +227,17 @@ public GoogleCredentials createScoped(Collection<String> scopes) {
  return this;
  }
 
+ /**
+ * If the credentials support scopes, creates a copy of the the identity with the specified
+ * scopes; otherwise, returns the same instance.
+ *
+ * @param scopes Collection of scopes to request.
+ * @return GoogleCredentials with requested scopes.
+ */
+ public GoogleCredentials createScoped(String... scopes) {
+ return createScoped(scopes);
+ }
+
  /**
  * If the credentials support domain-wide delegation, creates a copy
  * of the identity so that it impersonates the specified user;