Replace textContent references and <span class='foo'> to make pivot tabl...

...e work in IE8

Fixes #100

- IE8 uses "innerText" instead of the standard textContent.  We can just use jQuery to set the text consistently.
- IE8 seems to have a bug where `$("<span class='foo'>")` doesn't correctly create a DOM element.  Splitting it out into `$("<span>").addClass("foo")` works