Update bluebird to version 3.1.2 🚀

[greenkeeperio-bot]

Hello :wave:

:rocket::rocket::rocket:

bluebird just published its new version 3.1.2, which is not covered by your current version range.

If this pull request passes your tests you can publish your software with the latest version of bluebird – otherwise use this branch to work on adaptions and fixes.

Happy fixing and merging :palm_tree:

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The new version differs by 312 commits (ahead by 312, behind by 59).

• 74f56ff Release v3.1.2
• af57c33 Fixes #971
• b7a4bf9 Fixes #926
• c66c2ca Fixes #970
• 612ad75 keyword
• 0bc9bcd Fixes #963
• 6bd757e override generator coroutine function length property
• 0dc2861 Merge pull request #953 from timeimp/patch-1
• cbb37a8 Figure it should say that.
• d6fb325 Merge pull request #962 from chetbox/promise-longstacktraces-deprecated-docs
• bda9a30 Add deprecation to Promise.longStackTraces docs
• a4d0c43 Merge pull request #944 from petkaantonov/backport-disposer-docs
• 18707e2 move promise argument paragraph, simplify example
• 81f8b48 Update disposer.md
• 87ba788 Update "Error: expecting an array or Promise"

There are 250 commits in total. See the full diff.

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