Got working with nested forms

A solution for https://github.com/waynehoover/s3_direct_upload/issues/74

This allows you to use s3 direct upload without requiring a separate form.  To use with just an input tag within an existing form you will need to do a couple things.

Set the url for s3 uploader since it can no longer get it from the form
```js
  $("#myS3Uploader").S3Uploader(
    {
    url: '<%=S3DirectUpload.config.url%>'
  });
```
This requires a url to be set in your uploader config

You can then include a file input tag using the following helpers

```erb
<%= s3_uploader_hidden_fields%>
<%= s3_uploader_field callback_url: model_url, callback_param: "model[param_name]", id: "myS3Uploader"%>
```

However this will not work with the IE9 fix and I do not know anything about making it IE9 compatable