add a way to customize the load command to run loadHTML or pass additional parameters to loadXML

remove callable type hint because its not available in php 5.3

remove options from test to not break when using loadHTML on php 5.3 where only one parameter is expected

actually cause test to fail if code is removed

add comment and clean up test

add scanHtml method and allow to pass in libxml headers

try to fix coding style fixes

update libxml on travis to not fail the tests