Just installed it successfully
Download apk from the the net typing in whatsapp 2.11.315, a warning will come up but ignore it.
When it tries to install, a message will tell you that you need to change setting (if you have it set on in security), check the box in UNKNOWN SOURCES and make sure in the next pop up window you have the ONLY FOR THIS INSTILLATION checked. Now it should install!
Okay this still does not work but you then need to follow the next steps.
It will ask for you to update, do it!
Then repeat the same security steps as before, next it asks for a number. I have a tab s 10" and it has its own sim and number, enter these and it's up and running after the SMS.