Ans refactor

- Fixes issues #96 and #99.
- Moves sign in area link dividers to CSS instead of HTML.
- Disables sign-up/sign-in forms after signing-up/signing-in.
- Hides sign-up form when user visits sign in page when they are signed in.

**BEWARE** Please test before merging as I may not be aware of all potential dependencies tied to these changes.