Screenshot is broken in latest release

[ionelmc]

Problem fixture is not used properly (the function definition from global scope is used instead):

Traceback (most recent call last):
  File "/home/ci/.virtualenvs/3683c16e06ef68da57a4e65b87bf8940/local/lib/python2.7/site-packages/pytest_splinter/plugin.py", line 515, in _take_screenshot_on_failure
    splinter_screenshot_getter_png=splinter_screenshot_getter_png,
  File "/home/ci/.virtualenvs/3683c16e06ef68da57a4e65b87bf8940/local/lib/python2.7/site-packages/pytest_splinter/plugin.py", line 369, in _take_screenshot
    screenshot_dir = session_tmpdir.ensure('screenshots', dir=True).strpath
AttributeError: 'function' object has no attribute 'ensure'

[ionelmc]

Likely cause of regression is 21de5e4 (code being moved out from the function that had the proper fixture in its closure)

[bubenkoff]

should be solved in latest release