Sculpin bundles cannot depend on Guzzle

I'm starting to get into Sculpin, and I created a bundle to support oEmbed in posts and templates.

https://packagist.org/packages/bangpound/sculpin-oembed-bundle

I want to use Guzzle in my oEmbed library because it has a lot of features that will make my work simpler, in particular caching, service descriptions and events. However, I cannot simply add Guzzle as a dependency. If I use guzzle/guzzle:~3.7, there are conflicts because react/http depends on a lesser version of Guzzle. If I use guzzle/guzzle:~3.0 (to match react/http), there are conflicts because react/http depends only on sub-components of Guzzle.

I think the fact that sculpin's dependencies are packaged in a phar means that the embedded composer cannot switch out the guzzle subcomponents for the full library.

The only work around is to set up a composer.json file in my project and add sculpin as a dependency. Even then, I can only use guzzle 3.0.

So this presents a messy problem, I think. I suspect react/http is used to provide the built in Sculpin web server. (But I haven't verified this.) Personally, I could get by without react/http because I'm using PHP 5.4.... I'm probably digressing now!

Do you have any advice for this dependency version conflict?