Default Handler Implementation

[tzilist]

So this should tackle #10 .

Little bit of info on what is happening here,

The call to router will no longer return Some(RouteResult) and instead always returns a RouteResult. The router will fallback to the default_handler that is set. This allows us to use all middleware that are set in the middleware_base of the root router. In the example, you can try it and see that logging is now working for the fallback route.

I'm not going to lie, this particular PR was probably a bit above my Rust level and feels a bit hacky to me. Let me know what you guys think!

Also, special thank you to @tirr-c for his countless hours answering my non-stop questions ❤️

TODO:
I'd like to write some tests but I will wait until the final implementation to do so. Let's hold off on merging this at least until some tests are written 😄

[tirr-c]

This nicely addresses my suggestion on always-applied middleware at #61 (comment)! However, there are some points that we can get it better, so I left a suggestion.

Some thoughts:

• You can make params optional if you like. It's totally okay if you don't -- I'll do it then.
• This is an open question: if the path matched but the endpoint for our method is not there, what middleware should be run? In this case, we also have resource-specific middleware chain and actual wildcard matches.

[tzilist]

@tirr-c I've gone ahead and made params optional. Would you mind taking a look to make sure it looks ok? Most specifically at the head file. Just want to make sure this logic makes sense - my thought was if we did not find any params here that should be a 400 error. There also may be a better way to write this using method's instead of nested match statements.

[tzilist]

I've gone ahead and split apart the Router into BaseRouter and SubRouter to remove the need to delegate the default_handler around for no reason. I've created a trait called Router. The only downside is that there is some duplication between the at and middleware functions between BaseRouter and SubRouter.

[tirr-c]

I think trying to extract match information from default handlers is a bug in application code. One should know that there's no wildcard match in default handler. Maybe INTERNAL_SERVER_ERROR is better, or... should panic here? 😝

[tzilist]

Haha yeah...I am hesitant to panic but I did make it INTERNAL_SERVER_ERROR. I guess I could make it panic? I dunno what to do here 😢

[tirr-c]

You're very close!

[tirr-c]

LGTM, let's wait for travis!