Update zone.js to version 0.8.4 🚀

[greenkeeperio-bot]

Hello lovely humans,

zone.js just published its new version 0.8.4.

State	Update 🚀
Dependency	zone.js
New version	0.8.4
Type	devDependency

This version is not covered by your current version range.

Without accepting this pull request your project will work just like it did before. There might be a bunch of new features, fixes and perf improvements that the maintainers worked on for you though.

I recommend you look into these changes and try to get onto the latest version of zone.js.
Given that you have a decent test suite, a passing build is a strong indicator that you can take advantage of these changes by merging the proposed change into your project. Otherwise this branch is a great starting point for you to work on the update.

Do you have any ideas how I could improve these pull requests? Did I report anything you think isn’t right?
Are you unsure about how things are supposed to work?

There is a collection of frequently asked questions and while I’m just a bot, there is a group of people who are happy to teach me new things. Let them know.

Good luck with your project ✨

You rock!

🌴

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The new version differs by 15 commits (ahead by 15, behind by 3).

• ffb2ab1 chore: release v0.8.4
• bcd09a0 fix: stack rewriting now works with source maps
• 0e19304 fix: correct declaration which breaks closure
• 8f6ddf3 chore: release v0.8.3
• f742394 fix(zone): consistent access to symbol to work with closure
• 2e4cca5 chore: release v0.8.2
• 8322be8 fix(zone): fix #674, handle error.stack readonly case (#675)
• 2a7dd7b chore: release v0.8.1
• ef39a44 feat(task): add task lifecycle doc and testcases to explain task state transition. (#651)
• 76fa891 feat(error): remove zone internal stack frames in error.stack (#632)
• a63ae5f fix(example): Update counting.html (#648)
• 300dc36 fix(XHR): fix #671, patch XMLHttpRequestEventTarget prototype
• 8db0159 chore: release v0.8.0
• d3c59d0 chore: make type checking stricter
• 54c8d35 feat(TypeScript): support TypeScript v2.2.1

See the full diff.

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