Fixed bug with HTML5 style booleans causing parsererror

If you use a fixture with the new HTML 5 style boolean attributes (i.e checked, selected) with no ="checked" or similar, jasmine-jquery will not load the fixture due to a parsererror when making its JQuery Ajax request, as it isn't valid XML. This can cause a problem with certain mustache.js techniques, such as

    <input type="checkbox" {{#Checked}}checked{{/Checked}} />

This commit sets the dataType to be HTML when retrieving a fixture, because, well, it is, which seems to fix the issue.