Expand README.md a bit
Visibility tests deal with element state

As per the specification visibility should be handled underneath the
section “Reading Element State”.

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rename : visibility/0x0-pixels.html => element_state/0x0-pixels.html
rename : visibility/1x1-pixels.html => element_state/1x1-pixels.html
rename : visibility/display-block.html => element_state/display-block.html
rename : visibility/display-none.html => element_state/display-none.html
rename : visibility/visibility-hidden.html => element_state/visibility-hidden.html
rename : visibility/visibility-visible.html => element_state/visibility-visible.html
Add basic automation of visibility tests
Add more visibility tests
Fix syntax errors
Fix typo
Add test for visibility style on child node taking presedence
Add tests for dynamically hiding element, and INPUT @type='hidden'
Add display: none tests for child nodes
Add tests for display: none always taking presedence
Add tests for presedence and morphing
Add test for unclickable INPUT @type='hidden' element
Add test for untogglable checkbox
Add tests for hidden input interaction
Import test scenarios from Selenium not previously covered
Add more tests hiding elements using various techniques
Move tests out of visibility section
Add some experimental visibility tests
Fix syntax problem
Import overflow test from Selenium