Add automatic handling of NoSuchElement exceptions

NoSuchElement exceptions are sometimes thrown instead of
StaleElementReference exceptions. This can happen when the Selenium2
driver for Mink performs an action on an element through the WebDriver
session instead of directly through the WebDriver element. In that case,
if the element with the given ID does not exist, a NoSuchElement
exception would be thrown instead of a StaleElementReference exception,
so those cases are handled like StaleElementReference exceptions.

Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>