Tests: Remove QUnit start hook

Conflicts:
	test/data/testrunner.js
Tests: Simplify "testTimeout" option
Tests: Remove Sizzle intergration tests

Fixes #14818

Conflicts:
	test/data/testrunner.js
Build: Use jscs to check test helpers

Also fix issues found by jscs

Conflicts:
	test/data/testrunner.js
Build: Add lint task
Tests: Correct logic of a broken assertion
Tests: Improve jsonp tests

Since global variable for callback always would be equal to undefined value
it better to check for boolean instead
Tests: Move some of the Sizzle tests to selector
Tests: Copy Sizzle.contains tests
Tests: Copy Sizzle.uniqueSort tests
Tests: Add test for selectors with commas
Tests: Add more tests for Sizzle attributes
Tests: Copy some Sizzle combinators tests
Tests: Remove unused variables
Tests: Fix failing ajax tests in oldIE
Tests: Comply the style guide