Instruction update

[kcolwell]

I couldn't get this extension to work at all until I dug through the code and found the suites, default, context from one of your tests.

[christeredvartsen]

I don't usually use that specific feature context when testing, I always create a project specific context that extends the one provided by this extension.

This is also more of a core Behat configuration, so no need to specify that in the docs for the extension.