Error Message when file upload is too large

Noticed a JavaScript error in IE9, which was caused by the call to
requestAnimationFrame in loader.js. Added client side checking of spaces on room name when creating a new room (fix #1191). Added custom error message for when a file upload is too large (fix #1190).
This is unrelated to the actual PR, but is a legit fix for an issue with IE9 (and possibly other browsers) where https://developer.mozilla.org/en/docs/Web/API/window.requestAnimationFrame isn't available.