Pytest-splinter

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- respect splinter_make_screenshot_on_failure (bubenkoff)

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- use native selenium socket timeout feature (pelme)

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- pytest tmpdir_factory support (bubenkoff)
- depend on splinter 0.7.3, remove the previous status_code monkey patch (pelme)
- add option `--splinter-wait-time` to specify splinter explicit wait timeout (pelme)

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- ensure base tempdir exists (bubenkoff)

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- introduce splinter_browser_class fixture (bubenkoff, ecesena)

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- correctly handle zope.testbrowser splinter driver (bubenkoff)