Allow &frac12; and &#189; format for entities

I updated the tests to match the new entities. It should now ignore all entity formats that I'm aware of.

    &nbsp;
    &frac12;
    &#189;

I don't have PHPUnit installed as part of pear/globally so I couldn't run the tests, but I am running this in production code. But still, please double check that I wrote the tests right.