Rework flash messages and small tweaks for email verification

Closes #22
Removes unused lodash import
rm console.log in lib/flash
Make email addresses unique

Fixes #26
Fix #24: Don't send message when email didn't change and tweak email copy
Fix #25: Actually use "current password" in user settings

Also adds sync version of `User#comparePassword`
Closes #27: Implement "flash and redirect"-helper
Add columns
Close #17: Implement account deletion
Mount signup, login, logout router under specific paths
Destroy session when account is deleted
Bump deps
Initial draft of teamspeak verification