Allow Steps dependencies to be composable via PicoContainer
Description
In acceptance/integration tests is often common to have a lightweight container (Pico, Spring, Guice, etc ...) to configure the tests with.
A container-supported Steps instance should be composable (either via constructor or setter dependency injection) with components configured in the container.
Each container support will be contained in a separate optional module.
We start with Pico support, with other containers to follow.
