ElementProxy enhancements and fix for #65

[dtognazzini]

New methods:
wait_for_absence(timeout = nil)
wait_for_presence(timeout = nil)

Fix for #65

[ipmsteven]

maybe use is_absent to keep the naming consistent?

[ipmsteven]

do we need require 'timeout' at the top of element_proxy.rb

[dtognazzini]

No. Good catch. I'll remove.

[ipmsteven]

If the load_element is succeed, the check_absece method will return false. However in the Waiter.wait_for the check_absence will called again and again until the time expired. I think we should return false and skip the wait_for if the load_element is succeed.

[dtognazzini]

I don't understand. check_absence should only return true if loading the element failed, which indicates the element is absent. If loading the element succeeds, then the element is still present. We want to wait for the element to be absent.

[ipmsteven]

oh yes I got it. Thanks @dtognazzini 😁