Update flow-bin to the latest version � (#727)

Summary:
## The devDependency [flow-bin](https://github.com/flowtype/flow-bin) was updated from `0.114.0` to `0.115.0`.
This version is **not covered** by your **current version range**.

If you don’t accept this pull request, your project will work just like it did before. However, you might be missing out on a bunch of new features, fixes and/or performance improvements from the dependency update.

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**Publisher:** [mroch](https://www.npmjs.com/~mroch)
**License:** MIT

[Find out more about this release](https://github.com/flowtype/flow-bin).

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Your [Greenkeeper](https://greenkeeper.io) bot 🌴
Pull Request resolved: https://github.com/facebook/flipper/pull/727

Reviewed By: mweststrate

Differential Revision: D19288142

Pulled By: passy

fbshipit-source-id: 1285148e9e32660462e196923afbfaf2764bc04c

.flowconfig

@@ -35,4 +35,4 @@ untyped-import
 untyped-type-import
 
 [version]
-0.114.0
+0.115.0