Add support for removing cancelled bluebird3 promises from the cache.

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When a bluebird3 promise is cancelled it doesn't call any success/failure handles which means that it appears to be permanently waiting in terms of the cache and will be given out to every subsequent call. This is a problem as when you try to subscribe to the returned, cancelled, promise it rejects with a CancellationError so we end up with a poisoned cache. This PR checks if the promise can attach cancellation handlers and if so we attach the onFailure handler to clean up in case of cancellation

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The lint is now failing due to an update in https://github.com/medikoo/eslint-config-medikoo - how would you like the lint cases fixed?

[medikoo]

The lint is now failing due to an update in https://github.com/medikoo/eslint-config-medikoo - how would you like the lint cases fixed?

I've fixed this in master. Issue was related to recent eslint upgrade (v4 -> v5). Therefore merge, and lint should be ok

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I picked up the master changes and all the tests look good now

[medikoo]

Thank you, published with v0.4.13

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Awesome, thanks!