Simplify first-timer check-in process

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Right now checking in is a bit unwieldy for first-time visitors:

1. Find (small) check-in button on unfamiliar website
2. Click (small) Create Account link on login page
3. Create account with password, profile, etc
4. Checked in?

This process can probably be simplified and smoothed out. Some ideas off the top of my head:

• Maybe Check-in page language could from "login/create account" to "I've been here before/I'm new!"
• Laddr already displays the check-in button only during events; maybe we could take over more screen real estate with a simple "join your brigade!" form during those times?
• Redirect new members straight to some "Get started/find a project" content