assertion hangs within a `pull` callback, and errors silently ignored within any function callback for the API

See this question about the test hanging on assert http://stackoverflow.com/questions/26770345/mocha-with-nodejs-assert-hangs-timeouts-for-assertfalse-instead-of-error.

Also is it possible to report some errors happening in function callbacks. For example if I have a stream generator:

```
return _(function(push, next) {
cheers.scrape(config).then(function(result) {
push(null, result);
next(self.articleLinkStreamByPage(yazar, page + 1));
});
});
```

and any error happens within this function callback, eg: `self is undefined`, then it silently ignores and does some weird things, is that intended, or could it be fixed?

PS: I think these two questions are related, that if highland.js is silently catching and ignoring the errors, than `assert(false)`, will be catched as well, thus it causes tests to hang somehow?

Edit: Also If I have an error in the stream callback functions, the tests will hang no matter what I do.

Start by reproducing the hanging assertion and silently ignored callback error described in the issue, using the pull callback and stream generator examples. Trace how errors from function callbacks are handled and compare the behavior with the linked Mocha question; done means callback errors are reported and failed assertions do not leave tests hanging.

Written by the indexing model from the issue text.