Improve the regex expression for matching quotation marks in the elementAttributesAreValid test

[jessebeach]

The following regex expression in the elementAttributesAreValid test does not accurately capture missing or mismatched quotation marks.

//Element has mis-matched quotes
var quotes = element.raw.match(/\'|\"/g);
if (quotes && quotes.length % 2 !== 0) {
    test.add(Case({
        element: node,
        expected: (typeof node === 'object') && (node.nodeType === 1) && $(node).closest('.quail-test').data('expected') || null,
        status: 'failed'
    }));
    failed = true;
}

An even number of mismatched quotations will pass this test.