ported Contributing Guidlines with CLA from https://github.com/w3c/web-platform-tests/pull/261
adding license file, same as https://github.com/w3c/web-platform-tests/blob/master/LICENSE
fix doctypes

--HG--
extra : rebase_source : f8cfcfcb0dc0e936fb0eab3ce64c4d1eb93f4a0f
update to build tools changes (removed patched html5lib dependency)
merge
removed spec link (hook testing)

--HG--
extra : rebase_source : 7b752843e8415906a4b3eaef33c4b9695884682a
hg rm-ing in order to submit via gitHub pull request
revising test based on feedback from GT
revising test based on feedback from GT
revising test based on feedback from GT
revising test based on feedback from GT
added new ref file with numbering in name
adding tests for column-fill
removing links from reftests
removing links from reftests; ading links to tests
revising assertion
removing old ref file
revising ref to avoid the use of supporting images
revising ref to avoid the use of supporting images
revising ref to avoid the use of supporting images