Fix for "authentication credentials" error, + updated README file

Good day, Ruslan!
I have provided a fix for "authentication credentials" error,
which happens when you use login+password instead of token :

array(1) {
  ["detail"]=>
  string(45) "Authentication credentials were not provided."
}

(you already did this fix in the past, but it didn't appear at the latest version of rutubex.php

Also, I have updated an example at README file
( addVideo function requires a new argument, "adult" )

Thank you for your hard work, I admire you