Clean up membership language/routes

[easherma]

Some of the copy is a bit dated.

We also have pages floating around what we never fleshed content out on: https://chihacknight.org/membership/

We probably should have a more fleshed out section for membership, but maybe for now we can just clean up/hide the routes. Ideally we'd have a membership page with membership info + application, and another page with just the application that we can link to.