v0.3.1: Support OPTIONS, small fixes/adjustments

• Support OPTIONS method.
• Remove support for query string literals (e.g. /foo?myliteral) in favor of query keys, which support all of the same use cases.
• Run server by default on 0.0.0.0 instead of localhost.
• Fix: On failures decoding query parameters and bodies, return 400 Bad Request instead of forwarding to the next route.
• Fix: handle top-level routes like any other parent routes and actually apply guards and pass parameters to child routes.