Refactor/rewrite as middleware

[PAkerstrand]

This PR re-writes react-router-redial to work as a middleware. This allows it to be easily integrated with other middlewares, such as react-router-scroll.

Notable changes

• useRedial - New function for creating a React Router middleware. Takes the same options as the earlier RedialContext. Instead of calling <Router render={(props) => <RedialContext .../>}/>, we now use applyRouterMiddleware instead: <Router render={applyRouterMiddleware(useRedial(redialOptions))}/>
• The redial-map is now based on path from Route rather than the Component. This allows us to have multiple routes handled by the same component but with different props. On the other hand, if we want to retain the properties, this is no longer possible. Perhaps we should have a way to force the redial-props key?

Remaining work

• Right now the prevProps etc doesn't work any longer. How should we handle this? Move the state down to <RedialContextContainer/> instead?

• Update the documentation to highlight the new approach to render both on server and client.

• Create an example mixing useRedial with another router middleware

  render={(props) => (
    <RedialContext {...props} {...redialOptions}>
      <RouterContext {...props} 
          createElement={(Component, routeProps) => (
             <RedialContextContainer routerProps={routeProps}>
               <Component/>
             </RedialContextContainer>
          )
      />
   </RedialContext>
  )}

• Add tests for the util functions. Also, is there a way to gracefully fail rather than throwing?

• ... More?

[dlmr]

I do not think we need to do this here, redial should take care of this for us.

[PAkerstrand]

Reverted

[dlmr]

Thanks a ton, this looks awesome! 👍

Just a quick thought, what do you think about using camelCase for the new util files.

get-route-path.js => getRoutePath.js
find-route-by-component.js => findRouteByComponent.js
map-keys.js => createMapKeys.js

I will take a closer look at this tomorrow and play around with it a little.

[PAkerstrand]

Oh absolutely, just an old habit I guess. Renaming would make it more consistent!

[dlmr]

This works great, awesomely done once again! 👍

I will go ahead and merge this and release it as 0.3.0 soon!

I will add you as contributor in the README.md and package.json if you don't mind along with giving you write access to the repo.