[ and ] not allowed in callback.

[vitamink]

Is there any reason not to allow a callback to contain [ and ]?

I an JS plugin (CkEditor) which names callbacks like: CKEDITOR._.jsonpCallbacks[197] and this fails with the current build of WebApiContrib.Formatting.Jsonp.

This is easily resolved by changing CallbackValidator.cs as follows:
private static readonly Regex JsonpCallbackFormat = new Regex(@"[^0-9a-zA-Z\[\]\$_\.] (...many keywords follow...).

If this change is acceptable I can submit a pull request with modified code and a test.

Thanks.