Add cleanup for new block stream

[adrianmcli]

Fixes #81

[honestbonsai]

What's the reason for changing to Subject? I seem to recall an earlier discussion that we had on changing the Subjects to Observables, since you couldn't push your own events to an Observable it was safer.

[adrianmcli]

You need the Subject to be able to call .complete on it outside of the function. I suppose you could assign it to a temp variable by using its closure.

[honestbonsai]

@adrianmcli CI is failing

[adrianmcli]

For some reason, using Subject for fromPolling makes the tests hang so I have reverted to using Observable for now. But this also means that the stream doesn't automatically complete when cleanup() is called.

This might cause problems down the road, but I'm not sure what we can do at this point. I'm not sure why using Subject causes it to hang.

btw, when I say "hang", I mean getting the following at the end of successfully passing all tests:

Jest did not exit one second after the test run has completed.

This usually means that there are asynchronous operations that weren't stopped in your tests. Consider running Jest with `--detectOpenHandles` to troubleshoot this issue.

No output has been received in the last 10m0s, this potentially indicates a stalled build or something wrong with the build itself.

Check the details on how to adjust your build configuration on: https://docs.travis-ci.com/user/common-build-problems/#Build-times-out-because-no-output-was-received

Do note that this only happens on Travis, not locally.

[adrianmcli]

@honestbonsai I found this comment: jestjs/jest#1456 (comment)

And I basically just set maxWorkers to a high number (10 in this case) and then the test seems to pass. If this is satisfactory to you, then I think we should merge. If not, then feel free to revert to commit 69d3e54 and merge that instead. I'll leave it up to you since I'll be in the air tomorrow.

[honestbonsai]

Hmm still broken, I'll take a closer look if you're busy. @adrianmcli

[adrianmcli]

@honestbonsai I triggered a rebuild and it passed. It just didn't update on github.

[honestbonsai]

Ok that works for me then