mithril-stream: end does not work with more than 1 stream in the chain

[foxdonut]

When creating a dependent stream with map(), calling .end(true) on that stream does not work if there is more than 1 stream up the chain.

Expected Behavior

Calling .end(true) on a stream should work when there is more than 1 stream up the chain. See this flyd example and notice that in both cases, "three" is not logged.

Current Behavior

See this same example with mithril-stream, in the second case, "three" is logged when it should not be.

Context

Sometimes when creating a stream that "listens" to another stream, it is desirable at some point in the lifetime of the application to "stop listening". This should be possible using .end(true), even if there is more than 1 stream up the chain.