Moved test cases inside tests and separated out custom, level 1, level 2 and level 3 tests (but sadly duplicating test code)

--HG--
rename : conformance_tests/custom/basic.json => tests/conformance_tests/custom/basic.json
rename : conformance_tests/custom/basic_contains.output => tests/conformance_tests/custom/basic_contains.output
rename : conformance_tests/custom/basic_contains.selector => tests/conformance_tests/custom/basic_contains.selector
rename : conformance_tests/custom/basic_empty.output => tests/conformance_tests/custom/basic_empty.output
rename : conformance_tests/custom/basic_empty.selector => tests/conformance_tests/custom/basic_empty.selector
rename : conformance_tests/custom/basic_nth-last-child.output => tests/conformance_tests/custom/basic_nth-last-child.output
rename : conformance_tests/custom/basic_nth-last-child.selector => tests/conformance_tests/custom/basic_nth-last-child.selector