feat: Add more examples and cleanup

[trezm]

Adds more examples for common cases like JSON, auth, and route params. Also does some cleanup in the code that caused some breaking changes (for example with error handling.) Because of the breaking changes, we've bumped the version to 1.3.0, which is not yet published.

[trezm]

For the req/res stuff, see the comment above!

For your three points, we're actually already capable of handling much of that!

• Streams: This is pretty dependent on what underlying engine you're using (hyper, actix, etc.) but in hyper at least, you have direct access to the body object which is, in fact, a stream! So treat it as you want :)
• Multipart/form-data: Just requires a parsing library. Another good example opportunity though!
• Websockets: There's a thruster library for using socket.io, but perhaps this is another opportunity for a more simple ws example.