React Modals are not Node compatible

[d-reinhold]

When requiring pui-react-modals in a node environment (i.e. server side rendering), the following error occurs:

/Users/pivotal/workspace/apps-manager-js/node_modules/pui-react-modals/node_modules/classlist-polyfill/src/index.js:18
11:39:26 web.1     |  if ("document" in window.self) {
11:39:26 web.1     |            ^
11:39:26 web.1     |  ReferenceError: window is not defined
11:39:26 web.1     |      at Object.<anonymous> (/Users/pivotal/workspace/apps-manager-js/node_modules/pui-react-modals/node_modules/classlist-polyfill/src…
11:39:26 web.1     |      at Module._compile (module.js:456:26)

Perhaps we could investigate using a better classlist polyfill, or write our own (or use the underlying DOM API directly).