v4.0.0-beta.7

Changes

• Added support for <Redirect> as a child of a <Switch>
• Fixed a bug where <Switch> would always remount children
• Removed subscriptions to avoid unneccessary rerendering in every <Route>
• Added <Switch location> and <Route location> props so that "pure" route
  components can know when the location changes
• Removed location persistence across app restarts in <NativeRouter>
• Made docs easier to find in individual packages directories
• Split context.router into two parts: context.history and context.route
• Changed matchPath signature to matchPath(pathname, options)