Fix for ftu tests

The following error is returned when using the click() method: http://pastebin.mozilla.org/2247837
For this I have logged https://bugzilla.mozilla.org/show_bug.cgi?id=854887
This only happens when using click() so I have replaced click(), with tap() in line #199(in test_ftu_skp_tour.py) and in line #101(test_ftu_with_tour.py) as a workaround for this issue

I haven't replaced all the uses of click() , because tap() fails when the element is not visible or the user cannot interact with it.