Added support for http-interop/http-middleware 0.5.0 (No BC Break)

[michalbundyra]

We keep also support for http-interop/http-middleware 0.4.1. We use webimpress/http-middleware-compatibility to keep compatibility with all versions of http-middleware. So customer of the library can use any version of http-middleware and migrate at any time to the latest version.

composer.lock is currently with version 0.4.1 of http-interop middleware, so tests run with:

• lowest - 0.1.1
• locked - 0.4.1
• latest - 0.5.0

[weierophinney]

Thanks, @webimpress