add annotations for thrown exceptions

src/Generator/RandomGeneratorInterface.php

@@ -25,6 +25,9 @@ interface RandomGeneratorInterface
      *
      * @param integer $length The number of bytes of random binary data to generate
      * @return string A binary string
+     * @throws \Ramsey\Uuid\Exception\UnsatisfiedDependencyException if `Moontoast\Math\BigNumber` is not present
+     * @throws \InvalidArgumentException
+     * @throws \Exception if it was not possible to gather sufficient entropy
      */
     public function generate($length);
 }