no-url and autoProcessQueue may be conflicting

Hi,

# Problem

Looking at the README section for [Usage Without Automatic Posting](https://github.com/felixrieseberg/React-Dropzone-Component#usage-without-automatic-posting), along with the usage of ```postUrl: no-url```, my understanding was that I could simply POST the files using a separate mechanism. Or, in my own case, just use it as a file browser without POSTing at all.

However, not calling ```dropzone.processQueue()``` would mean that the empty progress bar overlay would be over the thumbnails indefinitely. It wasn't until I explicitly called ```processQueue()``` to a valid POST endpoint that the progress bar "completed" and was replaced with the check mark.

# Investigation

However, looking through the [comments in dropzonejs code](https://github.com/enyo/dropzone/blob/master/src/dropzone.coffee#L183) and the dropzone [documentation on enqueue files](http://www.dropzonejs.com/#enqueuing-file-uploads), it appears that ```autoProcessQueue: false``` is simply a mechanism to delay the POST until a future time. Perhaps via button, or some other user-triggered event.

With this in mind, I believe the ```postUrl: 'no-url'``` will not have the intended behavior as dropzone appears to expect. [This check](https://github.com/felixrieseberg/React-Dropzone-Component/blob/master/lib/react-dropzone.js#L54) in ```react-dropzone.js``` also suggests that a postUrl or drop/init event handler is necessary. If anything, the ```postUrl: 'no-url'``` assignment appears to be a workaround for this.

# Resolution?

I have a branch [here](https://github.com/ko/React-Dropzone-Component/tree/autoprocessqueue) with [the following commit](https://github.com/ko/React-Dropzone-Component/commit/24ff695fb8f02b6655e0c4d2943e8a1fad8992c0) to act as an example. Rather than a pull request, I figure this may require some discussion due to the scope of the potential change.

Thanks,
Ken

Start with the README's “Usage Without Automatic Posting” section and the check in lib/react-dropzone.js, then compare the linked Dropzone.js enqueue documentation with the example branch and commit. Determine the intended interaction between postUrl: 'no-url' and autoProcessQueue: false; done means the component supports file browsing or externally handled uploads without leaving the progress overlay indefinitely.

Written by the indexing model from the issue text.