Update react-router to the latest version 🚀

[greenkeeper]

Version 4.0.0 of react-router just got published.

Dependency	react-router
Current Version	3.0.2
Type	dependency

The version 4.0.0 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 react-router.
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.

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Version 4.1.0 just got published.

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Version 4.1.1 just got published.

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Version 4.1.2 just got published.

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Version 4.2.0 just got published.

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Release Notes

v4.2.0

Changes

Aug 23, 2017

• Re-run Redirect on props update (#5162 by @alexilyaev)
• Prevent remounts on routes with the same component in renderRoutes (#5430 by @artywhite)
• Case sensitive routes (#5438 by @paustria)
• Use direct imports in platform packages (#5095 by @ruiaraujo)
• Add optional otherProps argument renderRoutes (#5137 by @jharris4)
• Bump hoist-non-react-statics (#5347 by @roderickhsiao)
• 3x build speed improvements on CI (ea1212a by @timdorr)
• Use Jest for testing (172dc16 by @mjackson)
• Explicit error using Route outside of Router (#4939 by @eXon)
• react-router-native Link improvements (#4816 by @benstepp)
• aria-current on NavLink (#4708 by @JasonEtco)
• Make AndroidBackButton a generic BackButton component (#5295 by @DonnieWest)
• Access Link's underlying node via innerRef (#5294 by @danielberndt)
• Return null from react-router-native DeepLinking if children is undefined (#5278 by @seekshiva)
• Warn when using the history prop on a pre-configured Router (#5151 by @Aprillion)
• Fix memory leak in ConnectedRouter during server side rendering (#5203 by @klis87)
• Reorder NavLink activeClassName/className priority (#5109 by @carloluis)
• Change react-native BackAndroid to BackHandler (#5093 by @SeanGroff)
• Fix react-router-native StackRouter (#5071 by @kafein)