Fix Batman.setImmediate in IE10 - closes #578

In IE10, `Batman.setImmediate` becomes the native implementation `window.setImmediate`.

When calling `Batman.setImmediate`, the nature of `this` in JavaScript means that `setImmediate` was being called with `Batman` as the context, but IE10 expects it to be `window`.

## Solution

We wrap the native implementation in a tiny closure so that it always gets called with `window` as the context (technically `Batman.container`). This means it will always work without changing the `Batman.setImmediate` API.

## Review

@hornairs @snookca  
Paired with @nickjs