Please document on how to implement dependent features.

[SleeperSmith]

I'm sure there's a way to have, say, Feature A to be active only if Feature B is active?

Thanks in advance.

[mexx]

By now there is no build-in way to do this.

You can implement a behavior to check dependencies by your self.
An example of an implementation: https://gist.github.com/mexx/7462904

Currently I don't faced a situation where I needed dependency management, but I thought about it already.
A possible way to provide this functionality would be to use a marker interface IDependOn<T> and check the dependency tree when questioned about the state of the dependent feature automatically.