Combine 'any instance' cukes

`expect_any_instance_of.feature` and `any_instance.feature` both have the same Feature description, which makes navigating relish app confusing:

![any_instance_relishapp](https://f.cloud.github.com/assets/97257/927196/8362d63c-ff9b-11e2-9bbb-28371a1771a6.png)

To resolve this, I combined those files.

Additionally I would like to pose the question of whether it makes sense to combine `message_expectations/allow_any_instance_of.feature` with `method_stubs/any_instance.feature` ?